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An intensive study of waterfowl populations on a small block of agricultural land, Minnedosa, Manitoba;… Dzubin, Alexander 1954

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AN INTENSIVE STUDY OP WATERFOWL POPULATIONS ON A SMALL BLOCK OP AGRICULTURAL LAND, MINNEDOSA, MANITOBA Tne Breeding Biology and Production of Some Diving and Dabbling Ducks of the "Pothole-A g r i c u l t u r a l • Breeding Habitat In South-Central Manitoba by" ALEXANDER DZUBIN A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n the Department of ZOOLOGY We accept t h i s thesis as conforming to the standard required from candidates f o r the degree of MASTER OF ARTS •Members of the Department of ZOOLOGY THE UNIVERSITY OP BRITISH COLUMBIA A p r i l , 1954 AN INTENSIVE STUDY OF WATERFOWL POPULATIONS ON A SMALL BLOCK OF AGRICULTURAL LAND, MINNEDOSA, MANITOBA by Alexander Dzubin ABSTRACT The thesis embodies the r e s u l t s of a two-year study, 1952 and 1953, of the breeding biology and production of some diving and dabbling ducks on the " p o t h o l e - a g r i c u l t u r a l n region of South-Central Manitoba. The study area was a sec-ti o n and a half block of pothole (small slough) country nine miles south of Mlnnedosa, Manitoba. I t s knob and k e t t l e topo-graphy was c h a r a c t e r i s t i c of the region and i t s land use, c l i -mate, and vegetative cover was t y p i c a l of the southern aspen parklands. The objectives were to assess the waterfowl habitat, to determine species composition, productivity, reproductive e f f i c i e n c y , and to determine the environmental pressures as they applied to the waterfowl of t h i s habitat. Breeding pairs of birds were trapped, then, color l e g banded, painted, or neck banded i n order to be followed. Broods were color marked by the i n j e c t i o n of dyes into the eggs. Mallards were the most common species breeding here, making up 33.7$ of t o t a l composition, blue-winged t e a l with 23.3%, canvasback with 10.1%; baldpate, p i n t a i l , redhead, ruddy duck, 2 shoveller, gadwall, green-winged t e a l and lesser scaup made up the remainder. Populations of birds rose to peak figures during the f i r s t week i n May. Blue-wings arrived much l a t e r than canvasback or mallard. Newly hatched broods were seen from May 23 to August 8 i n 1952 and from June 2 to August 23 i n 1953. 94.1 breeding pairs of birds i n 1952 and 90.8 pairs i n 1953 produced 49.4 and 60.2 broods respectively. E f f i c i e n c y (brood/pair r a t i o ) of dabblers varied from .28 f o r p i n t a i l s to .85 f o r blue-wings. Mallard e f f i c i e n c y was .37 and .51 f o r the two years. Diver brood/pair r a t i o was higher than dabblers. The area of 1 square mile produced 331 young i n 1952 and 355 i n 1953. Average maximum brood size f o r a l l species and a l l age classes was 6.9. Reduc-ti o n i n brood s i z e with increase i n age was notedj Class I broods averaged 7.1, Class I I - 6.8, Class I I I - 6.4. Nesting studies indicated that c a t t a i l was the chief nesting cover followed by upland grasses, whitetop, bulrush, annual weeds, and others. 52.6% of a l l dabbler nests were recorded on road allowances, fence rows, or waste uplands, while 30.6 were found on pothole edges. The remainder were found on aspen-oak b l u f f s , willow rimmed potholes, and stubble f i e l d s . A l l divers nested i n the emergents i n potholes. 43.9% of a l l dabbler nests i n 1952 and 37.2% i n 1953 hatched successfully. Diver hatching success was higher, 67.7% i n 1952 and 64.5$ i n 1953. Predator losses were 3128% and 30.4% for dabblers but only 6.5% and 6.6$ f o r divers. Desertion and Intolerance, a g r i c u l t u r a l a c t i v i t i e s , flooding, freezing weather and dye loss accounted f o r the r e s t . Brood 3 hatching periods appeared to be l a t e r i n 1953. Weather plays an important r o l e i n making avail a b l e surface waters f o r breeding pairs and broods. Secondarily i t influences nest hatching success. More dry potholes were r e -corded, at comparable times i n 1952 than i n 1953. Pothole water l e v e l s were a l l higher i n 1953. A g r i c u l t u r a l practices influence waterfowl production eith e r immediately, through a destruction of nests and cover or through long term influences by encroach-ment on cover and conversion of waste uplands and potholes into crop lands. There i s danger of future drainage i n the region with subsequent loss of habitat. Predation was the chief cause of most of the nest destruction and undoubtedly had a marked ef f e c t on f i n a l production. The s p a t i a l requirements of breed-ing pairs i s not cl e a r . Blue-wing home ranges covered one-quarter of a section, mallards - one section, and canvasback -four sections. Aggressiveness varied i n i n d i v i d u a l pairs from time of day and from day to day. Management suggestions f o r the region included the creation of more l o a f i n g spots, through chemical treatment of vegetation or through a building of small r a f t s . Management practices only apply i f the pothole water areas are to be man-aged intensively. The concept of the community r e l a t i o n s h i p of potholes w i l l have to be taken into account before any f u t -ure drainage i s contemplated. * * # TABLE OF CONTENTS PAGE NO. Map of Southern Manitoba showing location of the Roseneath Study Area . . I A e r i a l Photograph of Roseneath Study Area II INTRODUCTION 1 Description of the Study Area 4 Location and time spent on project 4= Geology and S o i l s of the Region 5 Climate 6 Vegetative Cover 8 Pothole Vegetation and a C l a s s i f i c a t i o n of Water Areas 10 Waterfowl, birds, and mammals of the area . . . 13 Farming practices and Land Use 14 Methods and Techniques Adult bird marking and trapping 17 Brood trapping and colo r i n g by use of dyes . . . 21 Wager guage data 25 Results 25 Breeding population study 25 Species Composition 25 Breeding phenology and population changes . 30 Phases of the Breeding Season 34 Productivity of the Area 37 Pairs and broods per square mile 39 E f f i c i e n c y per pair 40 Brood sizes at fledging 41 TABLE OF CONTENTS (Cont'd.) PAGE NO. Potential Limiting Factors 44 Nesting Studies - 1952 and 1953 45 Weather, and water a v a i l a b i l i t y as l i m i t i n g factors 50 A g r i c u l t u r a l Practices and duck production . . . 58 Predation as a l i m i t i n g f a c t o r 64 Available t e r r i t o r y and s p a t i a l requirements of pairs as a l i m i t i n g factor . 66 Discussion of Results 78 ACKNOWLEDGEMENTS 86 LITERATURE CITED 89 * * INTRODUCTION The study of breeding duck populations which has evol-ved i n recent years has been a most important step i n the over-a l l management of waterfowl i n the four major flyways. I t s im-portance stems from the r e a l i t y that to manage any species we must f i r s t understand some of the basic ecology p e c u l i a r to that species. Furthermore, we must have a detailed f a m i l i a r i t y with the dynamics of the group i n i t s natural environment. The present study embodies the r e s u l t s of a two year project c a r r i e d out i n Manitoba on a t y p i c a l portion of a g r i c u l t u r a l land used as breeding habitat by ducks. Here, an attempt was made to understand some of the ecology of the waterfowl species breeding there and further to ascertain the dynamics of a given number of duck p a i r s . Across the wide aspen parklands of south-central Mani-toba l i e some of the f i n e s t waterfowl breeding habitat of the entire North American continent. Here i n a wide rectangular block stretching from Elkhorn and Neepawa i n the south, north to the Riding Mountain National Park, and thence west to Russel, are found the innumerable small sloughs, lakes and marshes to which ducks return yearly to breed. Here too are found the f e r -t i l e black s o i l s which each year give f o r t h t h e i r bountiful har-vest of cereal crops. In t h i s area of some four thousand square miles two crops, one of food cereals, and the other, waterfowl, grow and mature together each on i t s own apportionment. 2 Each spring as water areas become avail a b l e through the melting of snow, ducks wing t h e i r way northward seeking the f a m i l i a r breeding area. Here amidst the stubble of l a s t year's crops and the f i e l d s of broken black sod, the waterfowl p a i r s s e t t l e and remain on the many w a t e r - f i l l e d depressions to nest and r a i s e t h e i r broods. These water f i l l e d depressions are known as "potholes" to waterfowl b i o l o g i s t s . These small ponds on a g r i c u l t u r a l land compose one of the foremost duck breeding habitats of a l l our p r a i r i e provinces. The term "pothole* i s used here also to distinguish the small w a t e r - f i l l e d depression from the larger lakes and marshes which dot the t e r r a i n and which also add to the pot e n t i a l breeding area f o r ducks. I t had been known f o r many years that waterfowl did breed on the small p r a i r i e potholes of the aspen parklands (Thompson 1890, Shortt and Waller 1937, Hochbaum 1944, Cart-wright 1948). However i t was not u n t i l 1946 that the f i r s t sur-vey of the breeding pot e n t i a l of these areas was c a r r i e d out by the U.S. F i s h and W i l d l i f e Service. Since t h i s date yearly spring and summer surveys have been practiced by j o i n t teams of the U.S. Fish and W i l d l i f e Service, Canadian W i l d l i f e Service, Ducks Unlimited, P r o v i n c i a l Game Branches, and the Delta Water-fowl Research Station. The primary objectives of these survey teams have been to determine early trends i n : 1. The spring breeding population. 2. The production of broods. Then an attempt was made to a r r i v e at some tentative conclu-sions, regarding population s i z e s , d ensities, and changes i n 3 de n s i t i e s , which might be used i n the formulation of the yearly waterfowl hunting regulations. It was not u n t i l 1948 that a spe c i a l research project was undertaken to test and r e f i n e the census techniques. Twelve transects, consisting of approximately one hundred potholes each, were established within t h i s parkland habitat. These were censused every few weeks through the spring and summer by Hr. William K i e l , of the University of Wisconsin, who headed the project. On each of the twelve transects ten areas were chosen f o r special study and these were followed i n t e n s i v e l y through the entire season. This project was c a r r i e d out by K i e l u n t i l the autumn of 1953; i t w i l l probably be continued by other per-sonnel f o r some time to come. A year a f t e r the K i e l Project was i n i t i a t e d , Mr. Charles Evans of the University of Minnesota spent a f u l l summer on a small portion of t h i s pothole range, s e t t i n g up a study area at Minnedosa, Manitoba. There he studied brood movements and con-structed a c l a s s i f i c a t i o n f o r small water areas. Additional i n -formation was gathered on broods and preference of breeding adult waterfowl f o r potholes; brood mortality and dispersion; and productivity. (See Evans et a l . . 1952). The present project, established i n 1951, i s an endea-vour to study i n t e n s i v e l y the production, behaviour, and ecology of waterfowl on a r e s t r i c t e d area of a g r i c u l t u r a l land i n the aspen parklands. The study was o r i g i n a l l y formulated i n an a t -tempt to determine the actual seasonal requirements of breeding birds and t h e i r broods i n the pothole region of Manitoba and furthermore to elucidate some of the environmental factors a f f e c t i n g these waterfowl. S p e c i f i c a l l y the study aimed: A. To assess the pothole type as a waterfowl habitat. B. To determine the species composition, number of breeding p a i r s , productivity and reproductive e f f i c i e n c y of p a i r s . C. To examine and describe the environmental pres-sures as they apply to the waterfowl of t h i s habitat. DESCRIPTION OP THE STUDY AREA Location and Time Spent on Project The study area was the same as that chosen by Evans i n his work of 1949. (Evans 1949, 1952). I t i s a t y p i c a l block of pothole farming land having a t o t a l area of one and one-ha l f square miles. The area was alt e r e d during 1953 to include a section block with a half mile buffer zone around i t . In a l l , the study block contained four sections of a g r i c u l t u r a l land situated nine miles South of Hinnedosa, Manitoba. The block was given the name "Roseneath Study Area" because of the close proximity of the Roseneath Consolidated School. Two f u l l sum-mers and a portion of a t h i r d were spent here doing f i e l d work concerned with t h i s project. During 1951, August 12th to Sept-ember 6th was spent on the area. In 1952 the season stretched 1 < UJ X o I-< < NORTH DAKOTA MINNESOTA •I. Russell 2.Birtle 3iElkhorn 4. Rapid City 5. Forrest 6Brookdale Plate I Southern Manitoba aRldingMountains LOCATION OF THE ROSENEATH STUDY AREA Minnedosa, Manitoba (Adapted from Evans 1951) 7.l^ e epaw a or < H 2 O Roseneath Study Area Minnedosa, Manitoba R.C.A.F. A i r - P h o t o s A11730-69 A11617-111 Plate 11 ROSENEAjm^^ Minnedosa , M a n i t o b a o o 0 o ^ 0 O 0 ° O o o 0 <5= Adapted from R.C.A.F. Air-Photos: A I I 7 3 0 - 6 9 A11617 - III Potholes with open water Potholes without open water Hooded P.FR.A. Dugouts ^ P.FR.A. Dugouts Alex Dzubin - 1 9 5 3 — Roads • . Buildings 5 from Hay 8th to August 29th while i n 1953 i t was spread from A p r i l 1st to August 26th. Permanent quarters were established on a b l u f f i n the south-west portion of the block, i n the form of an army Nissett Hut. A l l f i e l d work was c a r r i e d on from t h i s point. Geology and S o i l s of the Region Most of western and south-western Manitoba i s an area of Cretaceous shales, superimposed over the limestones which occur i n the eastern part of the province. ( B i l l s 1938). In general, a l l of t h i s parent material i s covered over by a r e -l a t i v e l y t hick layer of boulder t i l l which i s composed of g l a c i a l d r i f t and minor amounts of modified d r i f t material. During the g l a c i a l period a continental i c e sheet moved from the region near James Bay across the granites, the limestones and the shales and c a r r i e d them f a r to the south. A further descrip-t i o n of the region i n c l u d i n g Odanah Municipality, wherein the study area i s located i s given by E l l i s ( l o c . c i t . ) . (Odanah Mun i c i p a l i t y l i e s i n what i s r e f e r r e d to as the Second Steppe Region of Manitoba, west of the great escarpment). From the 1900 foot to the 1550 foot contour the t e r r a i n i n the second steppe occurs as an undulating p l a i n of boulder t i l l with occasional terminal moraines. They have a knob and k e t t l e topography with numerous small lakes. The t i l l p l a i n area between the moraines varies from smooth to roughly undulating and i s charac-t e r i z e d by numerous depressions with meadow s o i l s and saline s o i l s . The study area i s some 1600 feet above sea l e v e l as taken from Topographical Survey Maps of Manitoba. I t i s located 6 same 10 miles north and west from the shore of former Lake Agassiz which can be traced from Forrest, Brookdale, and Nee-pa wa. The slope of the land i n the region i s south-eastward bat t h i s slope i s hardly d i s c e r n i b l e on the undulating t i l l p l a i n . The s o i l s of t h i s region are predominantly northern black earths or degraded black earths formed under a grass-land and aspen grove vegetation. Because of the knob and k e t t l e topography black earths, northern black earths, and either meadow s o i l s or swamp podzols, may ex i s t within a few rods of each other on exactly the same parent material. The eff e c t of r e l i e f on the formation of l o c a l s o i l types i s quite marked. Heavy r a i n and melting snow run-off may remove surface s o i l and deposit i t i n lower positions forming l o c a l deep accu-mulations of top s o i l s from the exposed k n o l l s . Climate Connor (1939) has compiled many of the meteorological records f o r Manitoba. Most of the following summary i s taken from h i s work plus that of Bird (1930) and E l l i s (1938). Much of south-western Manitoba i s dominated by P a c i f i c influences When not under the influence of A r c t i c airmasses. At Minne-dosa mean January temperatures vary between-9°F and +7°F with t h i s month being the coldest. J u l y temperatures range between means of 56° and 74° with frequent recurring hot days. The f r o s t free period i s less than 100 days, the l a t e s t f r o s t usually occurring i n e a r l y May and the e a r l i e s t i n l a t e August. 7 A general cool condition p r e v a i l s i n t h i s region of Manitoba due to the f a c t that a i r currents from the west cool as they r i s e to pass over the Riding Mountains. The p r e c i p i t a t i o n i n south-western Manitoba i s about sixteen inches per year or 1800 tons per acre. Most of the p r e c i p i t a t i o n i s i n the form of r a i n while the percentage of annual p r e c i p i t a t i o n which i s snowfall runs between twenty and twenty-five percent. At Minnedosa, the annual p r e c i p i t a -t i o n runs from seventeen to eighteen inches with snowfall from f o r t y to f i f t y inches: The following table taken from Connor (1939) shows the average amount of p r e c i p i t a t i o n f o r the grow-in g season i n four stations a l l within twenty-five miles of the study area. Table I Average R a i n f a l l f o r Growing Season, A p r i l to August Ho. of Tears Place R a i n f a l l Standard Percent of Record (to 1939) i n inches Deviation Average Ppt. 51 Brandon 8.82" 3.23 36 53 Minnedosa 8.49 2.34 27 51 Rapid C i t y 8.19 2.79 34 51 Treesbank (St. Albans) 8.76 2.57 29 Out of 153 days from A p r i l to August, Minnedosa has only 56 rainy days on the average. Total p r e c i p i t a t i o n f o r A p r i l and May i s about three inches while that of June and July r i s e s to 8 s i x inches. Of the t o t a l annual p r e c i p i t a t i o n 5% f a l l s i n March, 6% i n A p r i l , 10 to 11% i n May, 17% i n June and 14% i n J uly. Of i n t e r e s t , as f a r as water r e l a t i o n s h i p s of pot-holes are concerned, i s that a great deal of the p r e c i p i t a t i o n f a l l s i n June and July when t h i s additive runoff i s important i n maintaining high water l e v e l s . Also of some note, because of the influence of r a i n on pothole water l e v e l s , i s the f r e -quent occurrence of thunderstorms, a maximum of t h i r t y i n one summer being recorded f o r Minnedosa. Vegetative Cover The forest vegetation of Manitoba has been described by H a l l i d a y (1934, 1937). Bird (1930) describes i n more d e t a i l some of the b i o t i c communities of the aspen parklands of Mani-toba. H a l l i d a y ( l o c . c i t . ) places Odanah Munic i p a l i t y i n the P r a i r i e and Aspen Grove Section of the Grassland Region. This section according to E l l i s (1938) was o r i g i n a l l y a l l p r a i r i e , the p r e v a i l i n g type of vegetation being t a l l p r a i r i e grasses. However, an invasion of woodland i s taking place c h i e f l y i n the form of aspen groves about depressions and on b l u f f s . In the d r i e r s i t u a t i o n s bur oak i s found along with aspen and poplar while i n the more humid positions willow and poplar have become established. The majority of c u l t i v a t e d and well drained s o i l s , which are now sown c h i e f l y to wheat, barley, oats and f l a x , were o r i g i n a l l y grasslands of the T a l l Grassland type. 9 Bird, ( l o c . c i t . ) working i n an aspen parkland area 80 miles to the north-west of the Kinnedosa region, gives an excel-lent description of tree and other plant species found there. Conditions at Kinnedosa were somewhat d i f f e r e n t and the follow-ing plant cover description i s alte r e d to conform to the area change. The.dominant tree of the woodland i s the aspen, (Populus tremuloides). with accompanying f a i r stands of Mani-toba maple or box elder (Acer negundo). elm (Ulmus americana). bur oak (Quercus macrocarpa). and balsam poplar (Populus  balsamifera). In a l l cases the succession i s toward aspen. The shrub stratum of b l u f f s consists c h i e f l y of chokecherry (Prunus v i r g i n i a n a ) . saskatoon (Amalanchier s p i c a t a ) . snow-berry (Symphoricarpos o c c i d e n t a l i s ) , red-osier dogwood (Comas  s t o l o n i f e r a ) . rose (Rosa blanda). and hawthorn (Crataegus sp.). Snowberry i s the most common shrub of the fence rows, pastures and road edges. Uncommon shrubs are s i l v e r b e r r y (Eleagnus  argentea). highbush cranberry (Viburnum opulns americana), and pincherry (Prunus nigra). The herb and forb layer on the uplands i s composed of ne t t l e (Urtica g r a c i l i s ) . i v a (Iva  x a n t h i f o l i a ) . sunflower (Heliantbus maximillianus). monarda (Monarda f i s t n l o s a ) , torch flower (Liatrus l l g u l i s t . v l i s ) , white aster (Aster e r i c o i d e s ) , blue aster (Aster praealtus), goldenrods (Solidago m o l l i s : S. r i g i d a . S. canadensis), black-eyed susan (Rudbeckia serotina), and sage (Artemesia f r i g i d a ) . Wheatgrass (Agropyron r i c h a r d s o n i i . A. Sm i t h i i ) ; junegrass (Koeleria c r i s t a t a ) , bentgrass (Agrostis hyemalis), and needle-grass (Stlpa comata) were the o r i g i n a l grasses present on the area. However, at the present moment brome grass (Bromus inermus) i s the most common and widespread, growing on b l u f f s , along fencerows, roadsides and pothole edges. Also prominent on roadsides i s sweet clover (Melilotus sp.). An excellent description of the b i r d and animal l i f e of the aspen parkland also appears i n Bird*s work and s h a l l there-fore not be given here because of the s i m i l a r i t y i n fauna of the two regions. Pothole Vegetation and a C l a s s i f i c a t i o n of Water Areas The o r i g i n a l study area of l i square miles contained some 186 potholes of various types, permanency, and vegetative cover. A c l a s s i f i c a t i o n of these water areas was attempted following that established by the Pish and W i l d l i f e Service Personnel of Region I I I . This c l a s s i f i c a t i o n has been adapted from the works of Bach (1951) and Evans (1952). Bach, ( l o c . c i t . ) working i n the pothole region of North Dakota, arranged h i s water areas i n t o s i x types, mostly based on permanency or the length of time each depression held water through the year. The following des-c r i p t i o n of types i s adapted from h i s plan: °A W - Water areas of greatest s t a b i l i t y , having not dried up during time of man's settlement i n the state. Any area which w i l l perhaps hold water even i n years of extreme drought should be placed i n t h i s grouping. A "Permanent11 pothold. "B* - Water areas which normally hold water the year around. In cases of severe drought these areas may go dry. They are normally quite stable. A "Semi-Permanent" pothole. (In t h i s study r e f e r r e d to as a "Permanent* pothole). "C" - Areas which normally dry up during J u l y and Aug-ust. In periods of more than average r a i n f a l l they may hold water throughout the ent i r e summer. As a r u l e most dry up by l a t e J u l y and e a r l y August. A "Temporary" pothole. "D" - The very transient water areas. They hold water f o r a few days or weeks at most a f t e r the spring run-off and a f t e r f l a s h floods. During some years many are farmed. A "Transient" pothole. "E" - Han made areas, impoundments and water dugouts. They are usually deep, stable, water areas. "S" - The l e t t e r "S" has been used a f t e r a l l of the above to designate streams since there are streams i n a l l of the above categories. A further breakdown of potholes based on the dominant vegetative cover i s u t i l i z e d by the U.S. P i s h and W i l d l i f e Service i n i t s "Unoccupied Water Area Forms." These are shown as follows: A areas Large lakes with rocky shores or surrounded by trees. B and C areas - Plant cover 1 - Grass or Sedge 2 - C a t t a i l 3 - Bulrush 4 - Wooded 5 - Miscellaneous D areas 1 - Cultivated 2 - Stubble §~« Pasture 4 - Burned 5 - Miscellaneous E areas 1 - Ordinary dugouts 2 - Flooded dugouts For example a B2 area would be a permanent pothole with cat-t a i l predominating while a D2 area would be a transient pond in a stubble f i e l d . The following chart gives some indication as to the numbers of different types of potholes on the area. (Chart I ) . Evans (loc. c i t . ) has l i s t e d the various other plant species occurring i n the above pothole types. He gives an excellent description of the occurrence of each plant species and the average percentage of the vegetation zone i t covers. The conspicuous dominants of the potholes are whitetop (Fluminea festucacea), sedge (Carex spp.). c a t t a i l (Typha  l a t i f o l i a ) . bulrushes (Scirpus validus. S. acntus.  S. paludosus). yellow cane (Phragmltes communis). spike rush (Eleocharls palnstris), common rush (Juncus sp.), and fox t a i l (Hordeum jubatum). Of the many aquatics, common duckweed (Lemna  trisn l c a) , water m i l f o i l (Myrlophyllum spp.), pondweed (Poto-PERMANENCE B C D - E Total % of total Veaetation Size in acres! 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 size class O.OI - 0.19 8 8 5 6 13 4 0 20.51 0.2 - 0.39 i 60 6 2 1 i i 72 36.92 0.4 - 0 .59 3 i 25 i 2 32 16.41 0.6 - 0.79 1 2 5 1 9 4.62 0.8 - 0.99 2 2 1 i 6 3.08 1.0 - 1.49 4 4 i 4 i 14 7.18 1.5 - 1.99 6 2 8 4.11 2.0 - 2.49 2 1 1 4 2.05 2.5 - 2.99 1 i 2 1.02 3.0 - 5.99 3 2 i 6 3.08 6.0 - 8.99 i 1 .51 9.0 - 12.0 i 1 .51 T O T A L 22 13 5 10' 8 I 2 8 5 6 16 I 4 195 % of tota l 11.28 6.61 2.56 — 533: 4.11 .51 1.02 — 4.11 256 3.0E — 8.21 .51 2.0; OO.OC Chart I Permanence, vegetational c lass ,and size character ist ics of all potholes found on the Roseneath Study A rea - 19 5 3 . 13 mogeton spp.), bladderwort ( U t r i e u l a r i a spp.), and buttercup (Ranunculus sceleratns and Ranunculus t r l c h i o f l l n s ) are the most common species. Waterfowl, other b i r d s , and mammals The following species and nested on the area. Common Name Mallard Blue-winged Teal Baldpate P i n t a i l Green-winged Teal Shoveller Gadwall Canvasback Redhead Lesser Scaup Ruddy Duck Coot V i r g i n i a r a i l Sora r a i l P i e d - b i l l e d grebe Horned grebe American B i t t e r n of waterfowl and water birds bred S c i e n t i f i c name (Anas platyrhynchos) (Anas discors) (Anas americana) (Anas acuta) (Anas car o l i n e n s i s) (Anas spatula) (Anas Strepera) (Aythya v a l l s i n e r i a ) (Aythya americana) (Aythya a f f i n i s ) (Oxyura rnbtda .iamaicensis) (Pulica americana) (Rallus l l m i c o l a ) (Porzana Carolina) (Podilymbus podiceps) (Colymbus durltus) (Botaurns lentiginosus) 14 Mink (Mustela vlsoa); muskrat (Ondatra z l b e t h i c a ) ; weasel (Mustela frenata); skunk (Mephitis mephitis): coyote (Canis  latrans) were the most important mammals found here. Poten-t i a l predatory birds were the crow (Corvus brachyrhynchos): Red-tailed hawk (Buteo b o r e a l i s ) : Swainson hawk (Buteo  swainsoni): sharp-shinned hawk (Ac c i p i t e r velox): goshawk (Astur a t r i c a p i l l u s ) : great horned owl (Bubo virginianus) and long eared owl (Asio wllsonlanus). Farming Practices and Land Use Much of south western Manitoba was s e t t l e d by an i n f l u x of pioneers between 1870 and 1895. The land about Minnedosa, at t h i s time, was u t i l i z e d c h i e f l y f o r oat growing because i t was under the influence of the cooler conditions brought about by the Riding Mountains. Excellent crops of oats with heavy weight per bushel were grown, and the oat acreage i n the early years of settlement exceeded the wheat acreage. With the i n t r o -duction of early maturing v a r i e t i e s of wheat, during the f i r s t part of the present century, the wheat acreage increased. ( E l l i s 1938). This zone can be considered as excellent f o r mixed farm-ing. I t i s p a r t i c u l a r l y suited to the growing of barley and oats but the percentage of arable land on each farm depends upon the l o c a l topography and on the amount of land occupied by depres-sions and sloughs. Evans (1952) has calculated s p e c i f i c a l l y the land use of the 1% sections. These appear i n Table I I 15 below: Table I I Land Use of 976 acres at Minnedosa, Manitoba (After Evans 1952) Use Acreage % of Total Acreage Wheat, barley and oat f i e l d s 560 57# Permanent pasture 140 Fence rows, road allowance, aspen groves, broken land 160 11% Water, wet areas, potholes 116 VZ% This use remained the same u n t i l the f a l l of 1952 when a 25 acre plot of a grain f i e l d was fenced off and planted to brome grass and clover. This p l o t i s now u t i l i z e d as permanent pas-ture. Farming practices i n the v i c i n i t y of Minnedosa follow the three year r o t a t i o n plan. Two d i f f e r e n t cereal crops are planted i n consecutive years, and then the f i e l d i s l e f t to fallow f o r the t h i r d . The usual procedure i s to plant wheat i n a f i e l d a f t e r the fallow; follow t h i s by barley or oats the f o l -lowing year, and then l e t the f i e l d l i e fallow again. Sweet clover or a l f a l f a may be planted as crops, e s p e c i a l l y i f the farmer has any number of c a t t l e to feed. A chart showing the chronology of f i e l d work and u t i -l i z a t i o n of land on three hypothetical f i e l d s , A, B, and C, i s shown below. For a continuous use series follow through from A to B, to C. Chart I I Chronology of F i e l d Use on Three Separate Blocks Month F i e l d A Fallow - 1952 (To be seeded to wheat 1953) F i e l d B Wheat - 1952 (To be seeded to barley 1953) F i e l d C Barley - 1952 (To be fallowed 1953) Jan. Feb. Mar. A p r i l May June July August Sept. Oct. Nov. Dec. Not worked Grazed Spring c u l t i v a -t i o n , d i s c i n g , drag chain, seed* ing to wheat Weed spraying Cutting, stook-ing or swathing Combining Burning stubble and c u l t i v a t i n g Grazed Not worked Grazed Not worked Grazed Spring c u l t i v a -t i o n , d i s c i n g , seeding to barley Grazed Weed spraying Stubble burned or disced Cultivated, l e f t to fallow Cultivated Cutting and swath- Cultivated as ing required Cultivated Combining Stubble l e f t or may be burned Grazed Grazed Spring wheat seeding usually precedes spring barley seeding, and combining may be respectively l a t e r . The number of times fallow f i e l d s are c u l t i v a t e d depends on the number 17 of heavy rains which induce p r o l i f i c weed growth. These fallow f i e l d s are usually grazed throughout the year; other f i e l d s being grazed before planting and a f t e r harvesting. METHODS AND TECHNIQUES A great deal of the success of the project hinged on the marking and following of p a i r s and t h e i r broods. Also, the f i n d i n g of nests to determine preferred nesting s i t e s , hatching success, phenology of season and clutch s i z e s con-s t i t u t e d an i n t e g r a l part of the work. Wherever possible d i r e c t observations of unmarked p a i r s and t h e i r broods with the a i d of 8 x 40 Binoculars and a 20x Power Spotting Scope were used to supplement the notes on marked bird s . S p e c i f i -c a l l y , the methods to trap and mark birds are described below. Adult b i r d marking and trapping Markings f o r the d i f f e r e n t i a t i o n of one b i r d from an-other were applied i n various ways. Ducks which had been pre-viously trapped were marked by: 1. An aluminum U.S. F. & W. Service l e g band. 2. A colored p l a s t i c l e g band. 3. Paint or "Testor Aeroplane Dope* applied i n three coats to the t a i l , back, or 7th and 8th primaries. 4. A colored, p l a s t i c neck band stapled about the neck. A combination of the above methods was used with much success. The colored l e g bands were always applied i n conjection with the Fish and W i l d l i f e Service numbered band but the birds were only subject to e i t h e r one of the other c o l o r marking techniques. Colored p l a s t i c neck bands have the advantage of being quickly and e f f i c i e n t l y used when the duck i s trapped. They are v i s i b l e up to distances of 400 yards, and are a more permanent type of marker, l a s t i n g u n t i l the staples rusted, usually within s i x months. The p l a s t i c neck marker can be suc-c e s s f u l l y used on waterfowl i f the band i s wide enough so as not to allow the lower mandible or whole b i l l to be caught and i f the material i s not too s t i f f f o r t h i s causes the b i r d to move with some d i f f i c u l t y . P l a s t i c neck bands were used i n a va r i e t y of colors and combinations of colors during the 1952 season. Daring 1953 i n an attempt to coordinate neck band colors used i n Canada and the U.S.A. the Canadian W i l d l i f e Service issued green as the basic color pattern to be used at Minnedosa. White was the second color assigned. Various white patterns, c i r c l e s , crosses, ovals and s t r i p e s were glued to the green neck band, with a waterproof type glue. Other green neck bands were painted with white "aeroplane dope." None of the colored neck bands u t i l i z e d during the two summers was found seriously to a f f e c t or impair birds i n any way. Nesting f e -males returned to t h e i r nests a f t e r being neck banded. Simi-l a r l y drake movements did not seem to deviate excessively be-cause of the presence of a neck band. A f t e r banding, birds as a rule fought the neck band by throwing themselves about and t r y i n g to swim backwards out of the band. Within an hour most birds appeared to be accustomed to the band f o r they fed and 19 and swam about na t u r a l l y . However, l a t e r observation showed an excessive preening of the band by the banded adult. Aeroplane dope marked birds were colored with d i f f e r e n t colored paints, red, yellow and white being the most v i s i b l e . As previously noted, the 7th and 8th primary could be painted as could the back, neck or t a i l region of the b i r d . Three or four coats were usually applied with the a i d of a s t i c k or reed. Combinations of colors were used i n many cases to d i f f e r e n t i a t e one female duck from another. Sowls (1950) who perfected t h i s painting technique f o r waterfowl use, succe s s f u l l y marked and colored many nesting females at the Delta marsh. Certain d i s -advantages are, however, inherent i n t h i s method. "Dope" has a tendency to remain s t i c k y and wet on cold, damp days. The dry-i n g period on these days f o r one coat being as long as 15 min-utes. Another disadvantage was that the dope had a tendency to matt surrounding feathers, e s p e c i a l l y i f the b i r d was released when the paint was wet. Birds that were marked i n t h i s way could be followed f o r periods up to two months. However, most birds were able to preen o f f much of the paint and i t was there-fore d i f f i c u l t to follow movements during the breeding season. Maximum distance of observation extended from 200 to 400 yards depending on the condition of the painted area. Colored l e g bands were u t i l i z e d wherever possible be-cause i t was f e l t that should birds return to the area i n sub-sequent years they could be i d e n t i f i e d by observing the color combination of t h e i r bands. This has not proven true f o r many of the colored bands are l o s t and i t i s d i f f i c u l t to observe the legs of ducks except on l e a f i n g areas. Some color-banded birds were successfully i d e n t i f i e d on muskrat houses, rock p i l e s and exposed shore l i n e s with a 2Ox Spotting Scope. Female ducks were trapped on t h e i r nests by a frame drop trap, as described by Sowls (1949). A hand net was also used to capture nesting females with equal success. The trapp-ing of drakes posed a special problem and many hours of f i e l d time were spent t r y i n g to devise some means of capture. Drive trapping, bait trapping and padded muskrat traps proved of l i t -t l e a v a i l as did night shining with the a i d of a strong beam. Two drake blue-winged t e a l were caught i n 1952 by the use of an adaptation of the clover Seaf bait trap, ( i . e . , a trap made from three lengths of fencing wire bent i n the shape of a clover l e a f ) . The females of the drakes were f i r s t nest trapped and placed i n a small wire cage. This cage was then lowered onto a platform,in the centre of the bait trap. The drake would r e a d i l y go int o the trap to j o i n h i s mate. This method was not pursued further but holds great promise i n the trapping of cer-t a i n i n d i v i d u a l s . I t i s , however, tedious and time consuming and may therefore not be warranted i n any large scale project. During the 1953 season i t was found that drake mallards or drake p i n t a i l s would not enter a bait trap where a hand reared female was tethered. Perhaps the breeding condition of the female b i r d i s important i n governing the actions of the drake. Another trapping technique which was used with great e f f i c i e n c y daring the l a t t e r part of the 1953 season was the "boom trap." This i s a cannon-projected net trap which throws a net over a pa i r or an i n d i v i d u a l duck when they are on a l o a f i n g bar. D i l l and Thornsberry (1950) had developed t h i s trap early i n 1949 i n .order to trap geese. Later a modifica-t i o n of the trap by Black and Evans (1953) to use black powder instead of potassium chlorate greatly increased the safety f a c -tor. This trap as described by Black and Evans i s a double cannon trap which throws out a 40 x 25 foot net. Because t h i s trap was not u t i l i z e d u n t i l a f t e r June 5, 1953 only s i x females and f i v e males were trapped with i t . However i t holds great promise i n trapping s p e c i f i c p a i r s . Brood trapping and co l o r i n g by use of dyes The broods of most species of ducks were su c c e s s f u l l y marked by i n j e c t i n g colored food dyes into the eggs before hatching. The dyes would color the down feathers of the young and therefore d i f f e r e n t i a t e the brood from a l l others. This method as perfected by Evans (1951) was u t i l i z e d during both years. The dyes used were bought from the Warner-Jenkinson Manufacturing Company, St. Louis, Missouri. Three colors, B r i l l i a n t Blue F.C.F., Fast Green F.C.F. and Ponceau S.X. were t r i e d . The f i r s t mentioned dye, B r i l l i a n t Blue, was found to be l e t h a l i n every case. During the summer of 1952 some nine nests were p a r t i a l l y or wholly marked with the dye. In every instance chick mortality occurred and not one of the marked eggs hatched. Preliminary t r i a l s of t h i s dye at the University of B r i t i s h Columbia on chicken eggs did not r e s u l t i n any mor-t a l i t y . The f i e l d m o r t a l i t y perhaps resulted from some toxic! e f f e c t forming i n the dye during the i n t e r v a l . Concentrations of dye were the same as those suggested by Evans (l o c . c i t . ) . The dosages used were also s i m i l a r and appear i n the following Table I I I . Table I I I Optimum Dosages per Egg of Two Dyes Used i n the F i e l d (After Evans 1951) Species Approximate Egg Weight Dosage of Fast Green Dosage of Ponseau SX Blue-winged Teal 28 grams 0.12 ml. 0.19 ml. Green-winged Teal 29 grams 0.12 ml. 0.19 ml. Shoveller 39 grams 0.16 ml. 0.26 ml. Baldpate 43 grams 0.18 ml. 0.29 ml. P i n t a i l 43 grams 0.18 ml. 0.29 ml. Gadwall 47 grams 0.19 ml. 0.31 ml. Mallard 54 grams 0.22 ml. 0.36 ml. Redhead 62 grams 0.25 ml. 0.41 ml. Canvasback 64 grams 0.26 ml. 0.42 ml. However i t was found that dosages of Ponceau SX (Red) could at times be exceeded by 60$ of the recommended optimum and s t i l l produce a good hatching of young. Greater than optimal dosages of Fast Green FCF are not recommended because the optimal dosages given were found i n some cases to be near 23 the l e t h a l dosage. The following table, Table IV, gives an i n d i c a t i o n of the hatching success of color marked eggs f o r the two summer seasons. Although the average hatching success was only 71.4$ t h i s i s by no means the actual success figure as many eggs were l o s t to the toxic dye i n 1952. Improvements i n i n j e c t i n g tech-niques during the 1953 season increased t h i s f i g u r e to over 75#. The f i e l d k i t contained the following parts i n a small wooden box. 2 -2 ml. syringes with needles attached, r o l l e d i n c l o t h . 2 -spare No. 23 needles. 1 -rubber cork with pin protruding l / 8 B to make holes i n eggs. 1 -40 ml. serum bottle of Ponceau S.X. 1 -40 ml. serum bot t l e of Fast Green F.C.F. 1 -small bo t t l e of mercurichrome or alcohol. 1 -small bottle c e l l o i d i n or white aeroplane dope. 1 -portion of an egg holding crate. The syringes, needles, cork, and the dyes were a l l c a r e f u l l y s t e r i l i z e d by b o i l i n g . Syringes and needles were a l l s t e r i l i z e d d a i l y a f t e r each day's work, then wrapped i n cotton c l o t h . A l l eggs were injected within a week before hatching usually when the hen l e f t her nest to feed. An average clutch containing nine eggs could be successfully injected within 12 minutes. The steps i n marking a clutch are given below: A. Remove part of clutch from nest. B. Place eggs i n egg crate. (A small part of the egg may be painted with alcohol or mercurichrome before hole i s punched). TABLE IV Hatching Success of Color-marked Eggs - 1952 and 1953 Seasons Duck Species Number of Total Eggs * Clutches l o s t Number of Harked Eggs Harked Eggs Percent Nests Harked Harked to Desertion Harked Eggs Unhatched Hatched HarkEd Harked Nests 1952 1953 and Predation i n l o s t (Due to Clutches Dye?) Eggs Hatch-Canvasback 9 27 (36) 169 (8) 49 40 80 66.7% Redhead 4 10 (14) 79 (5) 28 16 35 68.6% Ruddy Duck 3 11 (14) 68 (5) 22 11 35 76.1% Scaup tm 2 (2) 18 - 7 11 61.1% Hallard 23 27 (50) 303 (26) 166 44 93 67.8% Blue-winged Teal 17 5 (22) 145 (10) 62 18 65 78.3% Shoveller 4 4 (8) 46 (3) 17 5 24 82.7% P i n t a i l 2 2 (4) 21 (1) 6 1 14 93.3% Baldpate 1 2 (3) 15 (2) 10 2 3 60.0% Gadwall 2 1 (3) 16 (1) 6 2 8 80.0% Green-winged Teal 2 1 (3) 18 (1) 7 4 7 63.6% Totals 67 92 (159) 898 a (62) 373 b 150 375 Average mark-ed Egg Hatch-c ing Success 71.4% *Not a l l eggs i n clutches were marked. c x 100 a-b 24 C. Punch small hole i n egg, 1/2" below small end, with needle i n cork. D. P i l l syringe with dye. E. Inject required amount of dye in t o egg by placing needle, at an angle, about l / 8 r t into hole. F. Seal hole with c e l l o i d i n or white aeroplane dope. G. Replace eggs i n nest and p u l l down over them. Hany of the hens with marked young were observed f o r long periods of time, i n order to determine i f any abnormal behaviour would r e s u l t because of the dye colors. In no one instance was any aggressive behaviour, by the female, noted toward the newly hatched, colored brood, even when young were of two col o r s . Ramsay (1951) found that i n domestic Muscovy Ducks, Mallards, and Canada Geese, both adults and the young l a r g e l y acquire, rather than i n h e r i t the a b i l i t y to recognize other members of the family to which they belong using c o l o r , voice, s i z e and form as cues. I t would appear, therefore, that the color of hatched young i s not too important i n recog-n i t i o n or i n the behaviour of the female. Ramsay and also Suhl and Ortman (1953) showed that an intense color change was most e f f e c t i v e i n producing an aggressive behaviour on the part of the female but only a f t e r colored young were s u b s t i -tuted f o r normal colored chicks. On one occasion two newly hatched canvasbacks were found dead on a nest. The young were both green i n color and were l y i n g atop s i x other unhatched eggs. Examination revealed both had apparently been pecked as there were severe hemorrhagic areas i n the abdominal area and on the back. The female was present on the nest at the time. 25 In t h i s instance the female may have pecked at her young be-cause of t h e i r intense green c o l o r or perhaps some predator may have caused the two deaths. Water Guage Data Each pothole on the study area contained one water guage, an eight-foot black spruce pole with a deep notch on one side. This notch was set at the September 5th, 1951 water l e v e l i n a l l potholes and subsequent readings were taken i n r e l a t i o n to i t . The pole was driven some 4 or 5 feet into the mud bottom of the pothole i n order to ensure a permanent marker. Weelsly readings of a l l water guages were c a r r i e d on i n conjunction with a weelsly waterfowl census of a l l water areas. Data were also c o l l e c t e d on c e r t a i n c l i m a t i c conditions such as r a i n f a l l , maximum and minimum temperatures, cloud cover and wind v e l o c i t i e s . Water l o s s or gain i n depth i n a l l pot-holes was l a t e r correlated with these c l i m a t i c conditions. RESULTS Breeding Population Study Species Composition. The breeding population of the Roseneath Study Area has been censused every year since Evans (1951) i n i t i a t e d h i s study i n 1949. The following Table V gives some i n d i c a t i o n of the numbers and average percentage of pairs breeding at the study area from 1949 to 1953. 26 TABLE V Calculated Number of Waterfowl Pairs per Square Mil e Roseneath Study Area 1949-1953 (1^ square mile population reduced to 1 square mile) Species 1949 1950 Year 1951* 1952 1953 Average No. Average Composition Mallard 30.4 22.0 36.0 32.7 30.3 33.7 Gadwall 2.3 2.0 2.0 2.0 2.1 2.3 Baldpate 5.4 2.7 8.0 8.7 6.2 6.9 P i n t a i l 5.4 3.3 7.3 4.0 5.0 5.6 G.W.T. 1.5 - 3.3 2.0 1.7 1.9 B.W.T. 17.7 27.3 20.7 18.0 20.9 23.3 Shoveller 3.8 8.0 2.7 2.0 4.1 4.6 Redhead 5.4 4.7 2.7 6.7 4.9 5.5 Canvasback 10.8 10.7 8.0 6.7 9.1 10.1 Lesser Scaup - 1.3 .7 1.3 .8 .9 Ruddy Duck 5.4 4.0 2.7 6.7 4.7 5.2 Total p a i r s / square mile 88.1 86.0 94.1 90.8 89.8 Coot numbers ( P a i r s / square mile) - 24.7 12.7 28.7 22.0 Data not comparable The species composition f o r mallards, blue-winged t e a l , and can-vasback has remained r e l a t i v e l y stable except f o r minor f l u c -tuations. Some of the other species have, however, fluctuated widely i n pairs present on the area, from year to year. Mal-27 lards composed over a t h i r d of the population while bine-winged t e a l followed with 23.3 percent. Canvasback were the most numerous diving duck making up 10.1 percent of the t o t a l duck numbers. A l l numbers and percentages have been taken from a "calculated number of p a i r s " f o r t h i s area. In c a l -c u l a t i n g numbers of breeding pa i r s of waterfowl the maximum numbers of pa i r s of any one species, observed during the weekly census, was u t i l i z e d as the breeding population. In-dividual drakes, who by t h e i r behaviour seemed to be paired, were counted as p a i r s . This maximum fi g u r e , which was u t i -l i z e d i n a l l subsequent pro d u c t i v i t y comparisons, was used as the base number because i t was f e l t that not a l l of the breeding p a i r s which u t i l i z e d the area were present during any one census period. The range of p a i r s c a r r i e d them be-yond the boundaries of the study area. I t was deemed neces-sary then, to calculate or assign a cert a i n number of p a i r s to each quarter section. Thus, a calculated number of pa i r s has been used as the t o t a l population of the block. Hochbaum (1946) noted that the r a t i o of males to females i n spring mig-rant f l o c k s was 1.02:1 f o r mallards, 1.09:1 f o r p i n t a i l s , 1.38:1 f o r the redhead, 1.89:1 f o r the canvasback and 2.01:1 i n the l e s s e r scaup. Because of these varying sex r a t i o s not a l l drakes were counted as p a i r s . Diving duck pairs were noted only i f both i n d i v i d u a l s of the p a i r were observed. Even dur-ing the nesting season several diving duck drakes might be found to accompany a single female. A small error may have resulted when a l l mallard drakes were counted as p a i r s . How-28 ever f i e l d observations seemed to indicate no large excess of unpaired mallard drakes i n the region, during the primary nest-ing period. Mr. William K i e l of the University of Wisconsin has obtained data, since 1949, on the species composition and yearly number of ducks inhabiting a 10-mile transect which bounds the study area on two sides. The transect i s l/4 mile wide and samples a t o t a l of 2|- square miles of t y p i c a l pothole country, due south of Minnedosa. Table VI shows the calculated number of waterfowl pairs observed on Ki e l ' s transect II from 1949 to 1953. The percent composition of the average number of pairs observed i s also given. Only a very crude comparison can be made between Tables V and VI. K i e l ' s censuses were not made i n a comparable way to the counts made on the study area. The main differences were that the transects were: 1. Censused only once and therefore the maximum number of pairs was not noted. 2. Censused at a period which was not phenologically si m i l a r to the study area census. 3. Corrected to have a 50:50 sex r a t i o i n any one year and i n a l l years, ( i . e . , a l l drakes were assumed to have hens). 4. Birds were not flushed from potholes by walking through a l l emergent vegetation. Table VI shows that there have been fluctuations i n the number of duck pairs per square mile from 1949 to 1953. However, as pointed out by Smith and Hawkins (1948), there remain f a u l t s i n current census methods that do not permit v a l i d comparisons on a narrow range of tolerance. Therefore, these fluctuations 29 TABLE VI Calculated Number of Waterfowl Pairs Observed on K i e l Transect I I , Newdale - Erickson D i s t r i c t , South Western Manitoba 1949-1953 (10 mile transect - l/4 mi. wide or 2& Square Miles) Species Year Average A v e ? a g e 1949 1950 1951 1952 1953 No. Composition Mallard 37 41 37 51 54 44.0 24.3 Gadwall 7 3 2 4 1 3.4 1.9 Baldpate 12 5 9 9 14 9.8 5.4 P i n t a i l 15 10 22 15 17 15.8 8.7 G. W. T. 2 1 1 6 2 2.4 1.3 B. W. T. 40 57 49 46 42 46.8 25.8 Shoveller 19 10 10 6 7 10.4 5.7 Redhead • 7 11 7 6 2 6.6 3.6 Canvasback 33 34 49 18 16 30.0 16.5 Lesser Scaup 2 9 5 6 12 6.8 3.8 Ruddy Duck 4 12 9 2 0 5.4 3.0 Total Pairs 178 193 200 169 167 181.4 Pairs/sq.mi. 71.2 77.2 80.0 67.6 66.8 72.6 Coot 108 59 66 47 59 67.8 Date at which census made 5/14+15 6/l 5/23+24 5/6-8 5/15 may not be r e a l . Spring water l e v e l s and pothole numbers have fluctuated somewhat from year to year but a good supply of sur-face water remained through the f i v e years. ( K i e l communica-t i o n ) . Therefore, the pote n t i a l breeding area a v a i l a b l e has remained about the same from year to year. 30 This s t a b i l i t y in population numbers might be ex-plained by stating that the carrying capacity of the pothole waterfowl habitat i n southern Manitoba has been reached. How-ever, both Hochbaum (1947a, 1947b) and Soper (1948) believe that the carrying capacity has not been reached possibly be-cause of the increased duck k i l l by hunting. Species like the gadwall, shoveller, baldpate, green-winged teal, redhead and canvasback do not increase yearly even though their "re-quired* breeding habitat appears to be present i n sufficient quantity. F a l l hunting pressure may be the controlling fac-tor. However, at present, the nature of specific requirements in breeding habitat for most species i s not well known and fur-thermore the effect of small, yearly habitat changes have not been studied. Therefore, whether or not a carrying capacity has been reached in the pothole country cannot be readily con-cluded. Although populations appear to remain relatively stable current census methods may not be sufficiently sensi-tive to measure yearly changes. Breeding phenology and population changes. The breeding season of a l l ducks can be divided into several behavioral phases, each with definite characteristics. Hochbaum (1944) has made such a division of the yearly patterns into the spring f l i g h t , courtship, nesting season, brood season, and the post breeding season. The following i s an adaptation of his work wherein a "typical" breeding season of a mallard pair i s des-cribed. Mallards in the Mississippi Flyway spend most of their 31 winters on some i c e free water area along the southern portion of the continent. Their l i f e here i s composed of feeding, r e s t i n g , wandering, and courting. The courtship period takes place during the f a l l migration, on the wintering grounds, and northward again onto the breeding grounds. An elaborate court-ship, as described by Delacour and Mayr (1945), takes place during p a i r formation. Pairs f l y northward u n t i l the female selects and s e t t l e s on one or several water areas. The male here sets out a t e r r i t o r y and protects a c e r t a i n area from a l l others of h i s species. Hochbaum (loc. c i t . ) notes that the t e r r i t o r y consists of: a) water area, b) adjacent nest-ing cover, c) food, d) l o a f i n g spot. The nesting and feeding area need not necessarily be on the t e r r i t o r y proper. The female of a foreign p a i r of birds i s always attacked when these birds i n f r i n g e upon a protected area. ( T e r r i t o r i a l f i g h t i n g of drakes may take place i n mallards but i s more c h a r a c t e r i s t i c of the t e a l s , widgeon, gadwall and the d i v i n g ducks). Copu-l a t i o n takes place during and preceding egg lay i n g . No e l a -borate nest building procedures take place, although an o r i g -i n a l small c a v i t y may be scratched, out of the ground. Nest-ing material from vegetation i n the immediate v i c i n i t y of the nest i s added during the egg l a y i n g period (Sowls, 1951). Breast down may be removed and placed i n the nest. One egg per day i s l a i d , usually during the early morning hours. The egg-laying period may vary from s i x to thirteen days depend-in g on the number of eggs l a i d . At the end of t h i s period incubation begins and may continue f o r 21 to 28 days, a f t e r 32 which time the young hatch. The male awaits the female on the t e r r i t o r y during egg laying and feeds with her when she i s o ff the nest ("Waiting Drake" of Smith and Hawkins, 1948). Other birds of t h i s species are not tolerated on the protected water area during egg laying. The male continues to wait on t e r r i t o r y during the f i r s t part of incubation but l a t e r may seek out groups of drakes and feed with them, usually, but not necessarily, o f f the t e r r i t o r y . ("Grouped Drakes" of Bue, 1952). The drake at t h i s time as well as during egg layin g may take part i n courtship f l i g h t s . A l l mallard drakes appear to abandon t h e i r t e r r i t o r i e s before the brood hatches. They then congregate i n flocks and r e t i r e to some large water area to molt. Unsuccessful females may also moult with these groups of males. Other females may j o i n courting groups, mate again and renest. (Sowls, 1949). Successful females remain with the hatched broods f o r a time varying between f i v e and nine weeks. During t h i s time the female leads the brood around to various feeding areas. The female remains with the young u n t i l they are nearly capable of f l y i n g and then leaves f o r the moult-ing grounds. The brood may remain together u n t i l f l y i n g age when they disperse. With the a r r i v a l of cold weather birds flock-up and leave f o r the southern wintering grounds. Breeding p a i r populations were censused weekly on the area, at the time of the c o l l e c t i o n of water depth data. Graphs I and I I show the changes i n numbers of various species through the 1952 and 1953 breeding seasons. (Again, a "calculated" ((or "indicated" a f t e r Bue 1952)) p a i r population figure has been u t i l i z e d where only p a i r s , and drakes which appear to be mated, are counted). A l l drakes i n groups of less than f i v e were counted as p a i r s . Larger groups were not counted as these i n d i v i d u a l s were probably birds on t h e i r way to the moulting grounds or at l e a s t , from outside the study area. Graph I shows the "indicated" breeding pairs of various species f o r the one-and-one-half section study block f o r 1952 while Graph II shows i t f o r 1953. The graphs demonstrate that there i s a yearly "peak" i n the population of each species and then a gradual "decrease" i n t o t a l p a i r s . The t o t a l number of pairs of a l l species rose sharply a f t e r A p r i l 29 i n both years, reached a peak on Hay 6 i n 1953 and Hay 13 i n 1952. However, there were more pairs present on A p r i l 29 i n 1952 than i n 1953, possibly because of the e a r l i e r spring. Mallards and canvasbacks appear to reach a peak soon a f t e r May 1 while the blue-winged t e a l population does not reach maximum figures u n t i l three weeks l a t e r . By the time the blue-winged te a l population has leveled o f f , mall-ard and canvasback pairs s t a r t to reduce. Any entire popula-ti o n census at t h i s time would not give a true picture of popu-l a t i o n composition. Two censuses, one f o r the e a r l i e r a r r i v i n g species and one f o r the l a t e r a r r i v i n g ones, would give a f a r better index of population composition. Other early a r r i v i n g species include the p i n t a i l , green-winged t e a l , baldpate, redhead, scaup, and American golden-eye while the l a t e a r r i v a l s were made up of shoveller, gadwall, ruddy duck and blue-winged t e a l . The 1953 breeding season extended for a somewhat longer period, f o r most species, than d i d the 1952 season. An early GFrapfc I Indicated breeding pair populations from weekly counts on the IT section area * l l O x 1952 Total indicated pairs ecies Mallard oBlue winged teal -•Canvasback 4 N . B . T D o e s not 10 20 30 10 20 30 10 20 30 10 20 30 10 20 30 APRIL MAY JUNE JULY AUGUST 1952 show maximum pair f igures X D a t a f f 9 m a census by .Kiel, Ward, Graph II Indicated breeding pair populations from weekly counts on tne Ii section area* H O T 195 3 1 0 0 + 10 20 30 10 20 30 10 20 30 10 20 30 10 20 30 APRIL MAY JUNE JULY AUGUST NB 195 3 Does not show maximum pair figures 34 spring with no inclement weather, i n 1952, may have resulted i n a more successful early hatch requiring l i t t l e re-nesting. However, the 1953 breeding season was some 10 days l a t e r , pheno-l o g i c a l l y , than the 1952 season and more severe weather with increased p r e c i p i t a t i o n ensued. Re-nesting may have been more widespread f o r several "peaks" appear i n both the t o t a l i n d i -cated p a i r s and the mallard numbers f o r that year. Another pos-s i b i l i t y i s that the peaks show wandering pairs that had not made a f i r s t attempt because of the weather. Phases of the Breeding Season. The lengths of egg lay i n g , incubation, and brood periods were determined for some of the species during the 1952 and 1953 seasons. Graph I I I gives the f i r s t and l a s t dates at which newly hatched broods of f i v e species, mallard, blue-winged t e a l , canvasback, red-head, and ruddy duck, were observed on the area. Table VII gives the f i r s t a r r i v a l dates, clutch s i z e range, incubation period v a r i a t i o n , and e a r l i e s t brood f l y i n g ages f o r most of the duck species found at Roseneath. Certain of the incubation periods and f l y i n g ages were not determined f o r several of the le s s common species. From an in t e r p o l a t i o n of the above chart and graph an estimation of the entire length of the hatching season i s seen to be: 1952 Hay 23rd to August 8th. 1953 June 2nd to August 23rd. These season lengths hold only i f we take the mallard as the e a r l i e s t breeding species and the blue-winged t e a l as the l a t -est. The hatching season f o r diving ducks i s shorter by a week. Graph i n First and last dates at which newly hatched broods were observed. Bars show the range of the hatching season for each of five species. Roseneath Study Area-1952 and 1953. 35 TABLE VII F i r s t A r r i v a l Dates, Clutch Size Range, Incubation Period V a r i a t i o n and E a r l i e s t F l y i n g Age of Duck Species Found at Roseneath A r r i v a l Dates Range i n Incubation Age i n Days 1953 Clutch Size Period of e a r l i e s t Variations f l y i n g young Mallard March 31 5 - 13 21 - 27 53 Gadwall A p r i l 30 9 - 11 21 - 25** 48* Baldpate A p r i l 23 8 - 11 23** 47* P i n t a i l March 31 5 - 10 21 - 25** 43 Shoveller A p r i l 28 7 - 11 21 - 25** 49 G. W. T. A p r i l 21 9 - 12 B. W. T. A p r i l 29 5 - 14 22 - 26 40 Redhead A p r i l 27 6 - 14 23 - 30 63 Ruddy duck May 5 5 - 12 21 - 27 65 Canvasback A p r i l 21 4 - 12 22 - 29 57 Lesser Scaup A p r i l 24 9 - 12 - 47* * A f t e r Blankenship et a l (1953). ** After Hochbaura (1944). The ruddy duck i s the l a t e s t hatching diver. For the species l i s t e d i n Graph I I I the f i r s t date i n 1952 at which newly hatched broods were seen preceded the f i r s t dates i n 1953 from three days to nearly three weeks. Mallard young were seen nine days e a r l i e r i n 1952, blue-winged t e a l eighteen days e a r l i e r , canvasback eleven days, redhead fourteen days, and ruddy duck three days. Last dates of observing newly hatched young were also l a t e r i n 1953. Toung mallards were seen 36 sixteen days l a t e r i n 1953, blue-winged t e a l fourteen days l a t e r , canvasback eight days, redhead nine days and ruddy duck f i v e days. Dabbling duck brood periods extended over a much longer time i n t e r v a l than d i d div i n g duck brood periods. An i n d i c a t i o n of the r e l a t i v e l y short time canvasback pairs were observed i s shown i n Graphs I and I I . Mallards and blue-winged t e a l drakes and p a i r s were seen f o r much longer periods into the summer. Hochbaum (1944) has also shown that, i n the Delta marshes, the range of the dabbling duck breeding season i s longer than that of the divers. As previously noted the 1953 breeding season appeared to be 7 to 10 days phenologically l a t e r than the 1952 season. A p r i l temperatures were abnormally high i n 1952 and plant blooms appeared several weeks early. As can be seen from Graph I I I f i r s t broods appeared much e a r l i e r i n 1952. This i s probably due to the nesting period s t a r t i n g l a t e r i n 1953. However, nesting may have started at the same time i n both years but by a d i f f e r e n t i a l nest destruction (e.g., by weather i n 1953) broods appeared l a t e r . The brood population on the 1^ section block may not have been large enough to deter-mine accurately any hatching v a r i a t i o n of one to two weeks. Yocum (1950) found a retarded hatching i n waterfowl i n 1948 i n Eastern Washington. He a t t r i b u t e s t h i s retardation to either flooding, because of an increase i n p r e c i p i t a t i o n , causing more renesting; to temperature as a retarder of the nesting period; and to decreased l i g h t and i t s e f f e c t upon the regulation of the sexual cycle. Cowan and Hatter (1949) work-ing i n central B r i t i s h Columbia also noted a l a t e r hatch i n 37 1948, when compared with the 1949 season. Two graphs that appear under "Pothole Study" i n a l a t e r section of t h i s thesis show that the 1953 season, i n comparison to 1952, was characterized by a somewhat lower maximum-minimum temperature and a higher r a i n f a l l . These weather phenomena, undoubtedly, do influence nesting seasons and i n d i r e c t l y brood hatching dates. Observations made on the area during the f i r s t two days of the 1953 duck hunting season, September 18 and 19, showed f i v e dabbler broods which had not yet attained f l y i n g age. Of the f i v e broods, three were blue-winged t e a l and two were mallards. At least four more ruddy duck broods, which were s t i l l on the area, were also incapable of f l i g h t . Of sixty-two hunters checked during the two day period, eight had shot birds which could not f l y ; seven f l i g h t l e s s blue-winged t e a l , two mallards and f i v e ruddy ducks were included i n t h e i r bags. PRODUCTIVITY OP THE AREA Productivity The productivity or number of young produced on the area was determined i n 1949 (Evans, 1951), 1952, and 1953. As previously noted, several counts of the breeding p a i r popu-l a t i o n was made early i n May and the highest number of breed-ing p a i r s , of any one species seen, was used i n a l l subseq-uent productivity comparisons. The number of broods was deter-mined by a complete "beat out" of a l l potholes on the area. Two such beat-outs occurred i n 1952 and three i n 1953. Evans (loc. c i t . ) had made one complete beat-out but had added f l y -i n g broods and broods appearing a f t e r his census. A l l broods noted during the second and t h i r d census, i n 1952 and again i n 1953, were s c r u t i n i z e d for duplications on the previous census. Thus, only broods which appeared to have hatched since the l a s t census were counted. Duplicate broods, i f any, were subtracted from the t o t a l , (e.g., I f a 2B mallard brood was recorded f o r the J uly 28th census and previously a IB mallard brood had been recorded on the J u l y 7th census, then only one, instead of two, broods would be counted i n the t o t a l . The IB mallard brood may have grown into the 2B brood i n the 3-week i n t e r v a l . There-fore, the r e s u l t s of the f i r s t and second census cannot be added without f i r s t c a n c e l l i n g out potential d u p l i c a t i o n ) . Blankenship et a l (1953) describe t h i s method of brood number subtraction based on a knowledge of brood growth rates. In t h i s way a cumulative number of broods can be determined f o r any area. One of the assumptions that must be made i n any producti-v i t y comparison i s that "egress of broods i s equal to ingress of broods." This assumption may not be v a l i d and c e r t a i n l y can-not always be noted. However, the Roseneath area appears to be a t y p i c a l block of land, s i m i l a r to a l l other areas i n the immed-ia t e v i c i n i t y . I f t h i s i s true broods should not u t i l i z e water areas on the study area to any le s s e r degree than other potholes of f the study block. Also, because of the writer's a c t i v i t i e s on the area, more broods may have moved off than moved on. Even then, a minimum production figu r e can be determined. Another assumption i s that the beat-out i s 100% e f f e c t i v e and a l l broods 39 are found. Again, t h i s may not always be so f o r many of the dabbler broods can run up onto the shorelines and in t o the grain f i e l d s beyond. Their behaviour, however, depends on the e x i s t i n g pothole water l e v e l s , i . e . , whether or not the water i s flooding into a l l emergent vegetation, making excellent escape cover. Table ¥111 shows the number of pairs and broods per square mile from 1949 to 1953. The number of broods per 100 pairs has also been c a l -culated. These are given as 56.5 broods/100 pairs f o r 1949, 52.5 f o r 1952 and 66.3 f o r 1953. Another way of expressing these census figures would be a r a t i o of broods to breeding pai r s or .56:1 f o r 1949, .53:1 f o r 1952 and .66:1 f o r 1953. This compares favorably with data obtained by Lynch i n Williams et a l (1949) who found a .53:1 brood to adult p a i r r a t i o i n Saskatchewan. Stoudt (1952) also working i n Saskatchewan found a .42:1 r a t i o of success. Kenneth Black, U.S.F. & W.S. Minn-eapolis (communication), believes that a success r a t i o of near .50:1 or 50 broods/100 pa i r s i s about the average f i g u r e ob-tained i n the pothole country. Work done by him and Evans at Waubay, South Dakota, seems to bear t h i s out. Some of t h e i r unpublished data, however, reveal a lower and highly variable productivity or %• Mallard productivity from year to year varied from 17% to 38$ i n the four years, while p i n t a i l varied from 18% to 49% and blue-winged t e a l from 89% to 44%. In each case 1953 was the most productive year. TABLE VIII Productivity of the Area - 1949 Through 1953 Species 1949* Pairs/square mj 1950 1951 1952 1953 1949* Broods/square mile 1950 1951 1952 1953 Mallard 30.4 22.0 36.0 32.7 9.3 10.7 13.3 16.7 Blue-winged teal 17.7 27.3 20.7 18.0 6.6 7.3 14.0 15.3 Canvasback 10.8 10.7 8.0 6.7 7.3 5.3 5.3 8.0 P i n t a i l 5.4 3.3 7.3 4.0 4.0 2.0 2.0 2.0 Baldpate 5.4 2.7 8.0 8.7 5.3 3.3 4.0 2.7 Shoveller 3.8 8.0 2.7 2.0 1.3 2.7 .7 2.7 Green-winged teal 1.5 - 3.3 2.0 1.3 2.0 1.3 .7 Ruddy duck 5.4 4.0 2.7 6.7 5.3 4.0 4.7 6.0 Redhead 5.4 4.7 2.7 6.7 4.7 4.7 2.7 4.0 Gadwall 2.3 2.0 2.0 2.0 .7 1.3 .7 .7 Scaup - 1.3 .7 1.3 - .7 m .7 Unidentified t e a l - - - 3.3 mm mm Unidentified M» .7 .7 .7 Total 88.1 86.0 94.1 90.8 49.8 42.7 49.4 60.2 * A f t e r Evans (1951) Number of Broods/100 pairs =56.5 a. 52.5 66.3 Data Not Comparable 9 Broods added from Dzubin (1952) report. 40 E f f i c i e n c y per p a i r A more important o v e r a l l f i g u r e i n the productivity of any area i s the number of broods produced by a c e r t a i n number of p a i r s . This might be termed the "reproductive e f f i c i e n c y " of each p a i r . It i s simply the number of broods observed divided by the number of breeding p a i r s . Table IX gives the e f f i c i e n c y per brooding p a i r f o r the 1952 and 1953 seasons, plus the data c o l l e c t e d by Evans. The e f f i c i e n c y of the three most numerous species, mallard,blue-winged t e a l , and canvasback varied markedly from year to year. Mallard varied from .24 i n 1949 to .51 i n 1953, blue-winged t e a l from .38 i n 1949 to .85 i n 1953, and can-vasback from .68 i n 1949 to 1.19 i n 1953. In each case, as i n the Waubay data quoted above, 1953 was the most productive year. The l a s t f i g u r e given f o r canvasback i n 1953 i s i n i t s e l f erron-eous f o r t h i s species r a i s e s only one brood per year. The e f f i -ciency per p a i r given i s greater than 1.0 probably because one or more broods moved onto the area while there was no corresponding emigration. This i s what probably occurred also with the 1952 census of ruddy ducks and the 1953 census of shovellers, both of which show e f f i c i e n c i e s greater than 1.0. Another f a u l t may have been an incomplete census of the breeding pairs of the area. This might happen i n the case of the ruddy duck and also with any of the diving duck species which have a very wide home range. With divers a more complete census can be made by counting number of nests on the area. Even though the census may have been incom-ple t e , diving ducks including ruddy ducks, have a much higher hatching success and brood/pair r a t i o than most of the dabbling duck species. Dataon nests w i l l be reported l a t e r . The lowest TABLE IX EFFICIENCY PER BREEDING PAIR or RATIO: BROODS/PAIR 1949 Species Number of Pairs Ratio Number of Pairs 1952 1953 Ratio Number of Pairs Ratio Mallard 30J.^ Blue-winged t e a l 17.7 Canvas back 10 o 8 P i n t a i l 5 . ^ Baldpate 5 . ^ Shoveller 3*8 Green-winged t e a l 1»5 Ruddy duck Redhead 5 . ^ Gadwall 2 » 3 Scaup -.24 .38 .68 .74 .98 .34 .90 .98 .87 .30 3b\0 20.7 8;o 7.3 8.0 2.7 3.3 H.7 2.7 2.0 .7 .37 .70 .66 .28 .50 .35 .40 1.74 1.00 .35 .0 32.7 18.0 £.7 ^.0 8.7 2.0 2.0 6.7 6.7 2.0 1.3 .51 .85 1.19 .50 .31 1.35 .35 .90 .60 .35 .54 41 dabbler e f f i c i e n c y , during 1952 and 1953, was .31 as recorded f o r baldpate, and the highest was .85 f o r the blue-winged t e a l . However, e f f i c i e n c i e s calculated f o r the les s numerous duck spe-ci e s may e a s i l y be biased by the immigration or emigration of only one or two broods. The average brood/pair r a t i o f o r the seven dabbler species during 1952 was .42 while i n 1953 t h i s f i g u r e had ri s e n to .60. More broods were, therefore, produced per p a i r i n 1953 than i n 1952. No averages have been calculated f o r the div-i n g duck species because of ce r t a i n i r r e g u l a r i t i e s i n the census methods. However i n each diving duck species e f f i c i e n c y was nearly always greater than i n any of the dabblers. Brood sizes at fledging The average brood si z e i n each age class has been c a l -culated f o r the area and f o r the surrounding pothole region. A l l brood counts taken i n the immediate v i c i n i t y of Roseneath and Minnedosa were u t i l i z e d i n the f i n a l determination. Only those counts which appeared to be made up of the en t i r e brood were u t i l i z e d , therefore figures may be somewhat higher than they a c t u a l l y were. Smaller broods may not have been counted as entire broods, when they should have been. Table X shows the average maximum brood s i z e s during the 1952 and 1953 seasons, f o r eacb of the three age classes. The t o t a l number of young i n each age class i s also given. The decline of brood observations with age does not i n -dicate emigration f o r many of the brood observations were taken o f f the area but i n the immediate v i c i n i t y of Roseneath. More TABLE X Average maximum brood sizes during 1952 and 1953 Class I Class II Class I I I A l l Ages No. of No. of Av. No. of No. of Av. No. of No. of Av. Total Av. Broods Young Size Broods Young Size Broods Young Size Number Size Mallard 89 561 6.3 52 354 6.8 46 286 6.2 187 6.4 Blue-wing 76 601 7.9 36 249 6.9 41 300 7.3 153 7.5 Canvasback 67 402 6.0 46 285 6.2 39 219 5.6 152 6.0 P i n t a i l 16 87 5.4 9 61 6.8 7 40 5.7 32 5.9 Baldpate 17 121 7.1 8 58 7.2 6 38 6.3 31 7.0 Shoveller 19 160 8.4 6 42 6.9 10 72 7.2 35 7.8 Green-wing 11 84 7.6 4 27 6.8 7 50 7.1 22 7.3 Ruddy duck 26 159 6.1 19 103 5.4 14 72 5.1 59 5.7 Redhead 38 283 7.4 22 152 6.9 16 98 6.1 76 7.0 Gadwall 10 81 8.1 4 27 6.8 2 15 7.5 16 7.7 Scaup 3 25 8.3 2 16 8.0 1 6 6.0 6 7.8 Total 372 (2564) 7.1 208 (1374) 6.8 189 (1196) 6.4 769 6.9 av. brood size observations were made, by the writer, during the early part of tbe brood season when most broods were Class l ' s than were made l a t e r i n the year. Wariness of broods may have also increased with age, lessening the chances of observation. The average brood si z e f o r each age class has been deter-mined by t o t a l i n g the average size f o r each species and then d i -v i d i n g by the number of species. There i s a progressive drop i n the average brood s i z e , 7.1 i n class I, 6.8 i n class I I , and 6.4 i n class I I I . This would indicate a brood mortality of close to I bird/brood. Blankenship (1952) working on some i s o l a t e d stock ponds i n North Dakota found the decrease i n brood si z e from class I to class i n t o be of about the same order. He was able to follow i n d i v i d u a l broods through to fledging. Work done at Roseneath on 22 i n d i v i d u a l l y marked canvasback broods showed an average decrease of .77 young/brood (or 17 young l o s t i n 22 broods). Most of the mortality appears to take place during the early class I stage. Causes of mortality were d i f f i c u l t to de-termine for very few of the dead young were recovered. The de-crease i n brood si z e as shown i n Table X appears to be greater between the class I I and I I I stages than between the class I and I I stages. This may only be a f a u l t of the census i t s e l f due to a congregation of the i n d i v i d u a l s i n the older age classes into one group or to an incorrect f i e l d determination of age classes. The number of young produced (class I) and the number that reach the f l y i n g stage class I I I are two d i f f e r e n t things. The l a t t e r can vary considerably from year to year, depending on conditions during the brood period, while the former may remain 43 the same. The number of f l y i n g young i s more important from the p r a c t i c a l standpoint as i t gives the number of birds a c e r t a i n area has contributed to the flyway as a whole. Evans ( l o c . c i t . ) had given a figure of 315 f l y i n g young produced from the Rosen-eath study area i n 1949. A l l figures i n class I I I have been lumped f o r 1952 and 1953 because of a low census figure f o r 1953. However, broods were smaller i n 1953 than i n 1952. Data indicated class I I I brood si z e was 6.7 i n 1952 while only 5.9 i n 1953. K i e l * s figures from the re s t of D i s t r i c t 8 i n Mani-toba showed an average size f o r c l a s s I I I broods as 7.3 i n 1952 and 6.6 i n 1953. ( K i e l communication). I f we u t i l i z e the f o r -mer figures of 6.7 and 5.9 f o r 1952 and 1953, re s p e c t i v e l y , and note that 49.4 broods were produced i n 1952 and 60.2 i n 1953, then, the number of young produced per square mile was 49.4 x 6.7 or 331 i n 1952 and 60.2 x 5.9 or 355 i n 1953. Therefore, even though the number of broods produced on the area d i f -fered during the two years the brood s i z e at f l y i n g age was such that the production of young was only 24 more i n 1953. The increase i n number of broods i n 1953 may have been due to the increase i n renesting i n that year when water conditions were more favorable and water l e v e l s remained high during the summer. However, certain inherent f a u l t s i n breeding p a i r census, e.g., turnover rate of p a i r s , cannot yet be c a l c u l -ated and t h i s may be r e f l e c t e d i n the f i n a l production f i g -ures. 44 POTENTIAL LIMITING FACTORS In most populations that are hunted workers continually t r y to determine the f a c t o r (or factors) that i s holding the population numbers to some l e v e l . Thus "environmental r e s i s -tance" i n any p r o d u c t i v i t y study i s the group of factors which hinder a population from reaching i t s density p o t e n t i a l . Cer-t a i n of the l i m i t i n g factors,which tended to delay and a c t u a l l y stop the attainment of the f u l l breeding pot e n t i a l f o r every p a i r at Roseneath, have been studied during 1952 and 1953. They are reported as " p o t e n t i a l " l i m i t i n g factors simply because t h e i r f u l l influence on the f i n a l production i s not c l e a r l y understood. Many more years of study, of each of the f a c t o r s , i s needed be-fore any conclusive r e s u l t s can be shown. Errington (1942) presented a s e r i e s of equations which could be applied throughout the nesting season to cal c u l a t e pro-d u c t i v i t y . Later Cartwright (1952) set up another s e r i e s of equa-tions which calculated number of young produced on a one square mile area when renesting took place. He used data from previous waterfowl nesting studies to model hi s examples. During the present study a t o t a l of 316 nests were found and the success of each was determined. The r e s u l t s of the nesting study are given p r i o r to the data on l i m i t i n g factors f o r i t i s the hatch-ing success of the nests which has a great deal of bearing on f i n a l production. Limiting factors such as water a v a i l a b i l i t y , a g r i c u l t u r a l practices, weather, predation and ava i l a b l e t e r r i -tory, w i l l be discussed l a t e r . 45 Nesting Studies, 1952 and 1953 Before launching d i r e c t l y i n t o the r e s u l t s of the two-year study i t should be emphasized that a proportional amount of time was not spent nest hunting i n each cover type. The amount of nest hunting was not dependent on the percent the cover type made up of the whole block. This would tend to give a biased sample of where nests were located. However, two complete coverages of a l l pote n t i a l nesting cover was made and i t was f e l t that a large percentage of the nests was found. Diving duck nests, which were nearly always b u i l t over water, were found very r e a d i l y . Another fa c t o r which influences the nest hatching r e s u l t s was the presence of the author on the area. However, at le a s t a minimum success percent can be c a l -culated. The immediate cover type i n which each nest was found was recorded. This was usually the dominant plant i n the v i c i n i t y . Table XI shows the nest numbers i n each cover type and the per-cent nest cover u t i l i z a t i o n . For the t o t a l nests of each spe-ci e s a percent occurrence i n each cover type was determined. Also the t o t a l number and percent of the t o t a l number of nests of a l l species i n each cover type has been calculated. M a l l -ards preferred upland grasses f o r nesting, c h i e f l y Bromus, Koelerla. S t i p a . Agropyron, and Agrostis. Fluminea or white-top was next as a preferred cover followed by sweet clover, annual weeds and aspen-oak b l u f f s . Blue-winged t e a l also pre-ferred upland grasses as nesting s i t e s . Only 7 of the mallard nests of 5.9# of the t o t a l and 2 or 4.5$ of the t o t a l blue-Nest numbers ineach cover type and percent nest cover utilization - 1952 and 1953. Immediate Nesting M A 1. B. W. T. p 1 N. s H V. B A 1 6 A P 6. W. T-c A It R. H. R H L. S. T L Po_pu|us-Quercus IQ (8.4) 1, (2.3) (3.5) Salix 7 (5.9) 1 (2.3) 1 1 10 (3-2L SyxDphQri-corpos 9 (7.6) 3 [6.8} 3 (16.7) 1 (7.7! 2 18 (5.7) Phraqmltes 1 (8) 1 (.3) Typha 6 (5.1) 34 66.7 14 (60S 17 567) 71 22.5) Scirpus 3 (25! 12 (235 8 34B; II 36.7; 34 (10.8) Cqrex 8 (6.7) 1 (23) 1 (7.r 2 (3.9) 2 14 (4.4) (Scofochloa? 16 8 (182! 4 4 308 3 (5.9) 1 (4.3) 2 (6.6 1 39 (12.3) Ekocharis 6 (5.1) 5 (114 1 12 (3.8) Upland Grasses 24 (2Q2 13 3 5 38.4 2 3 3 53 16.8) Annual Weeds It (92) 6 13.6) 2 11. i) 1 (7.7) 1 21, (6.6) Sweet Clover II (9.2) 4 (9.1) 1 (5.5) 2 18 (5.7) Stubble-Fa low Fields 7 5.9! 2 (4.5) 5 2718) , l 4 , (4.4) Total 119 4418 nooiioo.) 13 100) 7 4 4 51 23 30 3 316 (IOO.0 * Percent of nests of the species, in this cover type. ^Percent of total nests in this cover type. winged t e a l nests occurred i n stubble or fallow f i e l d s . Five of the eighteen p i n t a i l nests found occurred i n stubble f i e l d s but t h i s f i g u r e may be biased because an intensive search f o r such nests was made i n nearby stubble f i e l d s . Diving duck nests were confined to the emergent vegetation i n potholes and were found e i t h e r i n c a t t a i l , bulrush, white-top or sedge, i n order of preference. 66.7% of the canvasback nests were found i n c a t t a i l , 60.9% of the redheads used t h i s cover and 56.7% of the ruddy duck nests were found here. However, these data do not show what cover type was a c t u a l l y most avail a b l e to the birds. On the study area i t s e l f only 5 semi-permanent or B potholes had bulrush vegetation dominant while 13 had c a t t a i l as a dom-inant. Ho estimation of the ac r e a g e - a v a i l a b i l i t y of each cover type has been made. Williams and Marshall (1938) working i n Utah found that of 312 mallard nests found 65% were i n hardstem bulrush, 7% i n c a t t a i l , 7% i n salt g r a s s , 6% i n willow and 5% i n cane. Of 343 redhead nests i n the same study the record s i t e preference was 65% hardstem bulrush, 12% c a t t a i l , 11% a l l s o l i bulrush, 9% saltgrass and 2% cane. They have further calcu-lated a percent acreage use r a t i o s for each cover type which i s Qftiu-(percent of nests i n a cover). y(percent acreage of a coverj Hardstem bulrush comprised only 3% of the vegetation found at Bear River but 39% of a l l duck nests were found i n i t . Girard (1941) records s i t e preference of 267 mallard nests i n Montana as t a l l grass, 3B%; short grass, 26$; t h i s t l e s , 1B%; c a t t a i l s , 8%; and the rest i n various weeds and shrubs. 47 Table XII shows the number and percent of nests found i n various n e s t - s i t e locations. A l l diver nests were found i n the potholes themselves while most of the dabbler nests, 110, were found on road allowances, fence rows pastures or waste upland. A further 64 of the dabbler nests were found around the pothole edges or i n the emergent aquatic vegetation. Only 6.7% of these dabbler nests were i n stubble and fallow f i e l d s where they were d i r e c t l y exposed to a g r i c u l t u r a l a c t i v i t i e s . Girard ( l o c . c i t . ) noted the average distance to water of mallard nests was 118 yards. Distance to nearest water was determined f o r a l l dabbler nests but no average figure has been calculated. This average distance has l i t t l e or no meaning at Roseneath where the potholes are scattered at random over the t e r r a i n . Most nests were, however, within 75 yards of some sur-face water when they were f i r s t constructed. Table XIII shows the hatching success and f a t e of nests f o r both dabbler and d i v i n g ducks during the two years, while Graphs IV and V present the same data, graphically. Divers were much more successful than dabbling ducks. However, t h i s may not r e f l e c t upon the f i n a l production f o r a higher percentage of dabblers may renest. Cartwright (1952) has pointed out that even though the hatching success of a species may be low, subsequent renesting increases the f i n a l production. However, l i t t l e i s known of the yearly renesting percentages of the various duck species. Sowls (1949) showed that 13 of 66 hens marked renested. I t must be emphasized that nesting success and reproductive success are not the same. The Number of nests in various nest-site locations 1952 and 1953 Nest - Site Location DABBLE RS T 0 a 1 % of total dabbler nests DIVERS T 0 t ? % of total diver nests M A L. B. P N. f? v. ft Lr 1 G. C ft R H. R n L. S. A s p e n - O a k b l u f f s 10 1 II 5.3 Pothole edges a n d Emergent a q u a t i c v e g e t a t i o n 4 0 14 4 6 6 4 30.6 51 2 3 3 C 3 107 1000 R o a d a l l o w a n c e s , F ence rows,Posturei and waste upland 5 5 2 6 9 7 6 4 3 110 52.6 W i l l o w r i m med p o t h o l e s 7 1 1 1 1 0 4.8 Stubble and F a l l o w f i e l d s 7 2 5 14 6.7 T o t a l 119 4^ 18 13 7 4 4 20$ Hoo.o 51 2 3 3C 3 107 100.0 48 TABLE XEII Fate of Nests Dabblers Divers 1952 1953 1952 " "1953 No. % No. % No. * Wo. % Hatched Successfully 47 43.9 38 37.2 21 67.7 49 64.5 Predation Loss 34 31.8 31 30.4 2 6.5 5 6.6 Desertion and Intolerance 15 14.0 17 16.7 7 22.6 16 21.0 A g r i c u l t u r a l A c t i v i t i e s 7 6.6 7 6.9 — 1 1.3 Flooding - 2 1.9 - 4 5.3 Freezing Weather - 6 5.9 - - 0. Dye Loss 4 3.7 1 1.0 1 3.2 1 1.3 Total 107(100.0)102(100.0) 31(100.0) 76(100.0) l a t t e r i s f a r more important as i t shows f i n a l production. I t has been discussed previously under " E f f i c i e n c y per p a i r . " (Table IX). Sowls (1948), working at the Delta marsh i n Manitoba, had previously found an average hatching success of 9 species of ducks as 35$ of 206 nests. Canvasback had a 58$ hatching success, redhead 42$ while mallard hatched 33$ and blue-winged t e a l 35$. Kalmbach (1937) found a 49$ hatching success of 512 nests of 13 species i n Alberta and Saskatchewan. Kalmbach (1938), working i n North Dakota, also found 54.4$ of 351 nests successful i n 1936 and 69.3 per cent of 566 successful i n 1937. He l a t e r c o l l e c t e d a l l data on hatching success and reported 49 that of 7600 nests of thirteen species of ducks and the Canada goose, the average hatch was 60% (Kalmbach 1939). He also noted that nesting success was greater i n the second half of the sea-son than i n the f i r s t h a l f . Bennett (1938) found a 59.6$ hatch-ing success i n 223 blue-winged t e a l nests i n Iowa. Low (1945) i n a study of 160 redhead nests i n Iowa showed that 56.2% hatched. K i e l (1952) working i n Hanitoba, from 1949 through 1952, showed that the percent success of divers nests varied from 65.4% to 86.9% while dabbler success varied from 45.8% to 56.3%. Workers i n C a l i f o r n i a , H i l l e r and C o l l i n s (1954), have noted a much higher success f o r dabblers than divers. They give 85.2$ as percent nests hatched f o r mallards, 93.2% f o r p i n t a i l s , 90.3% f o r gadwall but only 45.0% f o r redhead and 32.0% f o r ruddy duck. These reveal a wide v a r i a t i o n traceable to l o c a l or seasonal variat i o n s i n environmental pressure. It w i l l be apparent also that hatching success on the study area was about median i n r e l a t i o n to the findings of other workers. Nest losses due to various factors are shown i n Table XIII and graphically also i n Graph IV and V f o r each of the two years. Most of the losses occurred to predation, c h i e f l y crow, skunk and ground s q u i r r e l . The d i f f e r e n t i a t i o n between nests destroyed by each of these predators i s d i f f i c u l t to determine so a l l were lumped. Also some nests which had been deserted may be l a t e r destroyed by one of the predators. Desertion and intolerance loss was second i n importance. Loss to predation was much more extensive i n dabblers than i n divers. However, percent desertion losses i n divers was more than i n dabblers. Sraph IV Percent hatching success and nest losses 1 9 5 2 PERCENT OF TOTAL NESTS 10 20 30 40 50 60 Hatchin succes Predation Desertionf Intolerance Agriculture Flooding Freezing weather Dye loss Hatching success Predation Desertion* Intolerance » Agriculture Flooding Freezing weather Dye loss DIVERS (31 NESTS) 10 20 30 40 50 60 PERCENT OF TOTAL NESTS 70 Graph V Percent hatching success and nest losses 1953 Hatching success Predation Desertion* Intolerance Agriculture Flooding Freezing weather Dye loss | Hatching success Predation! W//A Desertion* Intolerance Agriculture Flooding Freezing weather Dye loss I PERCENT OF TOTAL NESTS 10 20 30 40 50 60 DABBLERS (102 NESTS) DIVERS I (76 NESTS) + 10 20 30 40 50 PERCENT OF TOTAL NESTS 60 70 50 Very few of the t o t a l nests were l o s t to a g r i c u l t u r a l a c t i v i t i e s , flooding, freezing weather or dye l o s s . Farming a c t i v i t i e s such as plowing, burning and heavy grazing destroyed only 6.6% of the nests i n 1952 and 6.9% i n 1953. A l a t e snowstorm on May 11, 1953 destroyed s i x of seventeen dabbler nests under observation at that time. Also i n 1953 heavy rains during the f i r s t two weeks of June caused some flooding i n dabbler and diver nests which were near pothole edges. Dye lo s s was recorded only when the entire clutch was marked and was unhatched due to the dye. Marked egg hatching success has appeared previously. (Table IV). Weather, and water a v a i l a b i l i t y as l i m i t i n g factors The weather of the pothole region about Roseneath, which has been described i n the Introduction, plays a very important r o l e i n the governing of production. Primarily, the weather of any one year d i r e c t l y influences the surface water a v a i l a b i l i t y . Secondarily, i t i s important i n i n f l u e n c i n g the success of the waterfowl hatch c h i e f l y through the e f f e c t s of flooding and freezing. Table XIII i l l u s t r a t e s that during 1953 a small percentage of dabbler (1.9%) and diver (5.3$) nests were flooded. Although end production might not be influenced be-cause birds would renest, one can conceivably see that ex* cessive rains during the nesting period would reduce the num-ber of nests hatching. K i e l (communication) noted that a " d i s -proportionate number of mallard nests i n the egg l a y i n g stage at the time of heavy r a i n s , May 24-June 3, 1953 were unsucces-s f u l . " He further noted that "mallard nest h i s t o r i e s showed 51 that nests active during the period of sub-freezing tempera-tures and snow, Hay 11-16, 1953, were as successful as nests started a f t e r Hay 16th." Such was not the case at Roseneath where winds, exceeding 25 m.p.h. p i l e d snow on some upland nests, and caused 6 of 17 nests under observation to be deserted. Thus, i t may be hypothesized that weather could influence and produc-t i o n i f i n any one year a series of weather phenomena occurred ( i . e . , excessive r a i n , freezing weather f o r long periods, heavy h a i l ) which continually disrupted hatching success. Even so, i f a single catastrophe occurred and only 50% of the females renested a s i m i l a r drop i n production would be noted. At the present moment the d i r e c t influence of weather on production i n the pothole region i s not c l e a r l y understood. Several more years of study on nest hatching success, e f f i c i e n c y per p a i r , productivity and brood s i z e , correlated with the p r e v a i l i n g weather i s needed. The contribution of weather to the si z e s and depths of surface water areas i s indeed important as f a r as use by breed-in g waterfowl i s concerned. I f s u f f i c i e n t water i s a v a i l a b l e , on an area, to a t t r a c t breeding pairs then that area should contribute to the number of ducks produced i n any region. A study of water losses and vegetational changes of the potholes, brought about by fluctuations i n water depth, was made on the study area during 1952 and again i n 1953. The study i t s e l f was i n i t i a t e d i n order that more comprehensive data could be obtained about water losses i n c e r t a i n types of potholes. This would give waterfowl b i o l o g i s t s a greater i n -sight i n t o the types of water areas that can be expected to hold water f o r broods and the types that are subject to drying before they are of much use to broods. Likewise f l u c t u a t i n g water depths would influence growth patterns of submergents as well as emergent vegetation. Since some duck u t i l i z a t i o n of pot-holes depends on plant cover and food a v a i l a b i l i t y , a general study of changes i n vegetation was also made. Potholes obtain a l l of t h e i r water from p r e c i p i t a t i o n , either d i r e c t l y or i n d i r e c t l y . The snows of winter and the rains of early summer a l l add water to the depressions. Con-nor (1939) has apt l y described the e f f e c t s of free z i n g s o i l surfaces on run-off. He stat e s : Since there i s no water table over much of the p r a i r i e s and evaporation and stream flow continue to carry away surface water at a rapid rate u n t i l the sur-face freeze occurs i n the autumn, i t seems doubtful that the rains of August and September contribute much to the moisture of the layers near the surface i n the following spring. Moisture near the surface i n Octo-ber i s undoubtedly frozen, early or late; according to the weather of any given year and i t seems reasonable to suppose that t h i s may be freed i n a dry spring at a time when i t w i l l be avail a b l e f o r the roots of seedlings. Against t h i s may be of f s e t the occurrence of heavy ra i n s i n ear l y spring. F a l l i n g on a frozen s o i l with l i t t l e or no opportunity f o r penetration of the s u b - s o i l , such rains must be l a r g e l y run-off with freshets ... flooding tbe lowlands. Secondly water i s made availa b l e to potholes by sur-face and sub s o i l seepage of s o i l moisture, by d i r e c t flowage from connecting potholes, by sub-surface flowage or percolation from a pothole at a higher topographical l e v e l to one at a lower l e v e l and from d i r e c t flowage of water from melting snows i n the adjacent f i e l d s and tree-covered b l u f f s . Although d i r -ect addition of water by p r e c i p i t a t i o n , e s p e c i a l l y r a i n , would be small during the common shower, the additive ground runoff i a many areas i s large. Some potholes investigated by Mr. William Kiel and myself, near the town of Minnedosa, has added eight inches of water during a 20-minute thunder shower. Run-off from a pothole basin should, to a large extent, depend on: 1. Slope of the retaining basin i t s e l f , making the runoff swift or slow. If slow, allowing more of the water to be absorbed by the s o i l . 2. Vegetation of the basin surrounding the water area. 3. Absorption qualities of the s o i l and subsoil in the basin. 4. Actual quality and quantity per unit time of the precipitation i t s e l f . A severe thunderstorm with a quick runoff adds more water to a pothole than a day long drizzly rain, which i s soaked up by the surrounding s o i l . 5. Size of the basin i t s e l f . Atmospheric water vapour influences water loss of pot-holes by directly controlled evaporation rates. Cool moist winds following a day of rain would certainly not be conclus-ive to absorbing surface waters. Winter precipitation, in the form of snow, does per-haps play the greater part in the av a i l a b i l i t y of surface waters daring the spring breeding season. The quantity and quality of the snow f a l l i n g during the winter season i s ex-tremely important. Snow i s blown by the predominant north-westerly winds into tree-covered bluffs, pothole basins, fence rows, snow fences, pothole vegetation and road ditches, and l i e s here until melted in the spring. This melted snow runs 54 off into adjacent depressions and f i l l s them to create pot-holes or adds more water to permanent water areas. Many b l u f f s during A p r i l of 1953 had as much as s i x feet of snow p i l e d up within t h e i r centres or on t h e i r south-eastern extremities. Since most of the b l u f f s have a depression adja-cent to them the melting snow was made available to i t . The water a v a i l a b i l i t y of the 1953 season appeared to depend on two large snowfalls which occurred during the l a t t e r part of March. Farmers i n the region stated that snow f e l l as a blanket over f i e l d s , to a depth exceeding eighteen inches. With the coming of warm weather the snow began to melt, but could not percolate into the s o i l since i t was frozen, and therefore runoff was heavy to the surrounding depressions. It was these snowstorms near Minnedosa that saved potholes from drying up early i n the 1953 season. The summer or f a l l of 1952 was exceedingly dry and i t was believed that only a superabun-dant winter snowfall and/or heavy f a l l r a i ns could add enough water to potholes to a t t r a c t breeding pairs i n the spring (Dzubin, 1952). Thus weather may influence pothole a v a i l a b i l i t y and f i n a l l y production i n two d i f f e r e n t ways. F i r s t i n creating s u f f i c i e n t surface waters to a t t r a c t breeding pairs i n the spring and secondly, by ensuring that s u f f i c i e n t surface water remains f o r hatched broods to reach f l y i n g stage. The follow-ing data i s presented to show how variable t h i s water a v a i l a -b i l i t y i s at any comparable time during two seasons. Graphs VI and VII show the d a i l y maximum and minimum temperatures and p r e c i p i t a t i o n at Roseneath f o r 1952 and 1953, Gr-^ph V I Daily maximum and minimum temperatures and precipitation at the Roseneath Study Area, Minnedosa, Manitoba. May to August, 1952 APRIL MAY JUNE JULY AUG. 1952 TEMPERATURE IN °F. PRECIPITATION IN INCHES 55 respectively. The r a i n f a l l was heavier i n 1953 than i n 1952. Heavy June and August p r e c i p i t a t i o n kept water l e v e l s very high. Graph VIII r e f l e c t s the weather conditions f o r both years, f o r i t shows the number of dry potholes observed at weekly i n t e r v a l s f o r 1952 and 1953. By July 2nd, 1952 nearly a l l temporary areas had gone dry while at the same date i n 1953 35 s t i l l had water i n them. The heavy thundershowers of August 2nd and 3rd added enough water to many of the tem-porary areas so that only 32 contained no water by August 5th. Even during 1952 s u f f i c i e n t areas with water remained on Aug-ust 26th to ensure a successful brood season. By t h i s date most broods had reached f l y i n g age. No serious lack of water for broods was noted i n 1953, f o r a l l semi-permanent areas and some temporary waters were s t i l l a vailable to broods by the end of August. The number of potholes available f o r breeding pairs varied i n both years. May and June rains i n 1953 assured a continual surface run-off with only a maximum of 18 temporary potholes drying during the two months. However, i n 1952 very l i t t l e r a i n f e l l before June 15th and a maximum of 83 dry pot-holes was recorded on June 17th. The t o t a l number of pairs u t i l i z i n g the area reached a peak on May 6th i n 1953 and May 13th, 1952. (Graphs I and I I ) . However, more birds, (108 pairs) were recorded i n 1952 than i n 1953 (97 pairs) but fewer potholes were avail a b l e to the birds i n 1952. This might i n -dicate that the s p a t i a l requirements of the pairs using Rosen-eath were not jeopardized by the 50 dry areas on May 13, 1952. A s i m i l a r occurrence has been reported from the Caron pothole NUMBERS OF DRY P O T H O L E S f ro o o CD O 00 O O o ro o + IIIIIIIIIIIIIIIIII///////////////////////////A o -t-I (0 (O <0 m ui m W N " £ 5 ro ro 10 CO c to — v\\\\\\\\\\\\\\\\^ ^^ ^ ro o o O NUMBERS OF D R Y ? 0 T H O L E S o o H w H I 3 cr a> 0 o co a> CL 3 -» ? a c a> CL to *< o a> Q < 1 ex. ro £ Q £ CD-• cn 2. < Q CO O 56 country of Saskatchewan, where a reduction of water areas has taken place but an increase i n breeding pairs was noted. (Gallop, communication). Perhaps the s p a t i a l l i m i t a t i o n s would not become acute u n t i l only a cert a i n number of permanent areas were available. However, even then the degree of aggressive-ness may not be great. Workers i n the short grass region of Saskatchewan report 10 to 15 pairs of mallards u t i l i z i n g a 5-acre pond and apparently nesting successfully. (Gallop, l e t t e r ) . Some idea of the e f f e c t of d i f f e r e n t c l i m a t i c conditions on pothole water l e v e l s can be gained by an inspection of the following graphs. Graph IX shows a comparison of water l e v e l readings i n two potholes of d i f f e r e n t vegetative type while Graphs X and XI show a comparison of readings i n two potholes of d i f f e r e n t permanency. A l l s i x potholes have been chosen to show a "normal" reading. A l l pothole water l e v e l s rose sharply a f t e r May 20th, 1953 at the same time as heavy p r e c i -p i t a t i o n was recorded. (Graph VII). Water l e v e l s remained high i n 1953 u n t i l July 1st when they again started to recede. The 1952 l e v e l s were d i f f e r e n t i n that water l e v e l s receded u n t i l July 1st, when a r i s e was noted and again receded u n t i l the end of August. In a l l cases, except one (B2 AREA .8 acres) the May 12th l e v e l was higher i n 1952 than i t was i n 1953. Sub-sequently the 1953 l e v e l was always above the 1952 one. Since most of the rains do occur during May and June (Connor 1939) pothole l e v e l s should be expected to be high during those months and continually lower daring July and August when l e s s Graph. IX A comparison of Water Level Readings i n two potholes of different vegetative type A p r i l Kfey June July August #May 12th readings reduoed to "0" Sraph X A comparison of Water Level Readings i n two potholes of d i f f e r e n t permanency f A •" "* 1953 16 I I I I I I I I I I I I I 1 1 I 10 20 30 10 20 30 10 20 30 10 20 SO 10 SO 30 A p r i l May June July August •raph XI & comparison of Water Level Readings i n two potholes of d i f f e r e n t permanency precipitation f a l l s . It i s perhaps the regular recurrence of the June rains that ensures a plentiful supply of water for breeding pairs and broods. No true comparison of water level readings of two pot-holes can be made for the depths, vegetation, size, exposure and basin size i s never the same. However, Graph IX does show the similarity of water loss between two potholes with almost similar sizes but different vegetative cover. In both years a somewhat larger amount of water was lost in the B2-AREA. If this area i s compared to the readings on the B2-AREA, Graph X and the Bl-AREA, Graph XI, a remarkable similarity i s noted even though sizes d i f f e r . However, the death decrease in the smaller areas i s greater. Graph X compares two potholes at different permanency, the C2-AREA going dry much earlier than the B2-AREA. However, depth of the two was not the same, the C2-AREA being much shallower. More violent fluctuations in level occurred in the less permanent area. Water loss was always more, but water gain was also more. Graph XI again compares two potholes of different per-manency both .4 acres in size. The less permanent area, CI, gained more water in 1953 than did the Bl-AREA. Subsequently the changes in waterlevels were almost identical until the Cl-AREA became dry. Water levels in the CI pothole, dropped more sharply than they did in the Bl pothole. In general then, i t can be stated that during the study period there has been no indication of water scarcity acting as 58 a l i m i t i n g factor to waterfowl nest establishment or brood sur-v i v a l . A g r i c u l t u r a l Practices and Duck Production A g r i c u l t u r a l a c t i v i t i e s influence the pot e n t i a l water-fowl production either immediately through a destruction of nests and cover, or through long-term influences by an encroachment on cover, and a conversion of waste uplands and pothole water areas into crop land. The magnitude of the immediate influence varies with each year and i s not permanent. The long-term en-croachment of farm lands into wet land habitat i s permanent and means the destruction of habitat. Can waterfowl and a g r i c u l t u r a l products both be raised and u t i l i z e d i n any one region without serious c o n f l i c t ? This question i s one of the foremost problems confronting waterfowl managers throughout the western provinces. On some lands water-fowl have caused severe crop depredation as has been pointed out by Mair (1953), C o l l s (1951), Gavin (1953) and Leitch (1951). However, this c o n f l i c t has been mostly during the early f a l l when ducks congregate on large bodies of water and feed i n the surrounding crop lands. Crop depredation i s a problem on the breeding grounds, but not during the breeding season. The problem on the breeding grounds takes, perhaps, another form. Waterfowl, across the aspen parklands and grass-lands of the P r a i r i e provinces, do u t i l i z e the small water areas of the a g r i c u l t u r a l region as breeding habitat. Here then the problem of whether a g r i c u l t u r a l a c t i v i t i e s do c o n f l i c t mater-59 i a l l y with waterfowl production i s formulated. As previously noted, farming practices can harm water-fowl production. Direct influences may be tabulated as those practices which might destroy nests, young, or breeding habi-tat during the breeding season. These are: (1) Clearing land (cutting brush and plowing uplands). (2) Burning (stubble and waste areas). (3) Seeding and the summer fallowing of stubble. (4) Grazing, e s p e c i a l l y overgrazing. (5) Haying operations. (6) General disturbance of breeding p a i r s by a l l of the above operations. During two years of observation, nest losses due to farm-ing practices have been only a small percent of t o t a l nest destruction. Table XIII shows the nest losses of divers and dabblers f o r 1952 and 1953. 6.6$ of the t o t a l dabbler nests were l o s t to farming practices i n 1952 and 6.9$ i n 1953. Diver nest loss was l i m i t e d to 3.2$ i n 1952; t h i s was only one nest l o s t through grazing of a pothole and subsequent desertion of the nest by the hen. Even here renesting may occur and there-fore no serious influence on duck production would take place. However, i n d i r e c t l y , some of the farming practices l i s t e d above, es p e c i a l l y burning i n t h i s d i s t r i c t , destroys nesting habitat and does burn some nests. Spring burning of pothole edges and of waste uplands i s quite common throughout the Minnedosa d i s t r i c t , e s p e c i a l l y dur-ing a dry spring. F a l l burning i s also common but i s again dependent on the p r e c i p i t a t i o n of the region at that time. Stubble f i e l d s , road edges and sometimes pastures may also be put to the torch. Thus a l l these potential nesting areas are l o s t and birds must subsequently nest i n other cover. Predators, c h i e f l y crows, then cause most of the nest destruction. Cul-t i v a t i o n and plowing are important only when the ducks nest i n stubble f i e l d s which are to be seeded to grain and must be worked. Table XII shows that only 6.7% of the t o t a l dabbler nests were found i n stubble or fallow f i e l d s , thus the poten-t i a l l o s s i s not a serious one. The e f f e c t s of overgrazing of potholes edges and a v a i l -able nesting cover on duck usage of potholes i s not well under-stood. Bue et a l (1952) showed that ducks i n the South Dakota Stock Pond region preferred l i g h t l y grazed to heavily grazed nesting cover. Also, ponds with grass type shorelines, i n l i g h t l y grazed sections, were u t i l i z e d by broods three to four times as much as those ponds with mud shorelines i n overgrazed areas. Bennett (1937) working i n Iowa found that blue-winged teal did not nest i n overgrazed pastures, while ungrazed pas-tures were u t i l i z e d more. Skunk and badger populations i n -creased abnormally i n areas protected from grazing. He noted that grazing any pasture unit to capacity would be b e n e f i c i a l to both ducks and farm economy. Work by Evans et a l (1952) i n Manitoba has shown that overgrazing may change the vegetation of potholes and i n d i r e c t l y influence duck use. Excessive tramp-l i n g by horses and c a t t l e may create a mudhole where a pot-hole existed previously. Emergent vegetation may be overgrazed and trampled into the mud. Such areas occur c h i e f l y about farm 61 buildings and around potholes used f o r watering c a t t l e . How-ever, th e i r use by pairs f o r l o a f i n g spots greatly exceeds those areas which are only l i g h t l y grazed. Waterfowl may be benefited by a g r i c u l t u r a l practices by making available waste grains f o r food during the breeding season and by the creation of l o a f i n g bars on pothole edges, through moderate grazing. As pointed out by Evans et a l (loc. c i t . ) moderate grazing would stop the attainment of a choked white-top pothole which would be the climax stage. Potholes thus grazed would remain as open areas either i n bulrush or c a t t a i l and would perhaps be of more use to breeding waterfowl. However, unless c e r t a i n potholes are overgrazed to the extent where l i t t l e or no vegetation i s a v a i l a b l e , they are of l i t t l e use as l o a f i n g spots f o r p a i r s . The only advantage of creating areas of bulrush or c a t t a i l would be to assure more nesting cover f o r divers and also to increase escape cover f o r broods. These seem to be i n excess at the present moment. The continual encroachment of a g r i c u l t u r a l a c t i v i t y onto waste uplands and road allowances w i l l undoubtedly lead to a reduction i n the potential nesting areas f o r birds. Each year more cle a r i n g of land i s seen. Prices of grains during the l a s t decade have been good and farmers have put more marginal land under c u l t i v a t i o n . It seems inevitable that at some f u t -ure date fence rows, aspen-oak b l u f f s , road allowances w i l l a l l be cleared and the land might well contain no nesting cover, ex-cept f o r the grain stubble. This perhaps w i l l depend to a large extent on the economic po s i t i o n and pressures exerted by a grow-62 ing country on the farmer. When and i f more food cereals are required, most marginal lands w i l l undoubtedly come under the plow. As a r e f l e c t i o n of the r e s u l t s of economic pressures and subsidies on waterfowl breeding habitat, one need only look at the pothole-agricultural regions of Minnesota, South Dakota and North Dakota. Schrader (1949), Schoenfeld (1949), Kimball (1953), and Peterson (1952), a l l give excellent accounts of the drainage programs ca r r i e d out by the S o i l Conservation Service i n each of the above-mentioned states. As Peterson (loc. c i t . ) points out i n a study by Evans and Nord (1952), i n South Dakota 1% of the potholes were annually l o s t through drainage and a t o t a l loss of 16$ to date f o r western Minnesota's pothole area i s recorded. In f i v e years a t o t a l of some 10,700 potholes i n South Dakota were eliminated. Kimball (1953) has more recently stated that at least 32,000 potholes or 63,000 acres of prime breeding habitat are annually being l o s t to drainage i n the three mentioned states. As previously stated, i f economic pressures warrant and subsidies to drain potholes i n Canada are given, then a large portion of the Canadian pothole breeding area i s i n jeopardy of being t o t a l l y and permanently destroyed. Drainage i s being c a r r i e d out i n Canada, although to a l e s s e r extent than areas to the South ( C o l l s , 1951). Conditions i n the Minnedosa pothole regions may not be conducive to large scale drainage. Excess summer r a i n s , shallow s o i l s and quick runoff may only r e s u l t i n more s o i l erosion, i f the depressions are drained. Certainly, some of the smaller temporary areas could 63 be drained without seriously a f f e c t i n g waterfowl production. At the present time l i t t l e i s known of the actual breeding pair and brood requirements i n terms of water areas. A long term study of the d a i l y and seasonal use of a l l water areas by pairs and the r e l a t i o n s h i p of one water area to another series i s needed before conclusive data on drainage p o s s i b i -l i t i e s i s formulated. However, current land use, economic pres-sures, and monetary returns w i l l again govern the i n t e n s i t y of drainage. Waterfowl habitat of the future might conceivably be only those marginal areas which cannot even be used f o r a g r i -culture. At the present moment certain b e n e f i c i a l r e s u l t s might be achieved with pothole drainage i n the removal of congrega-t i n g areas of depredating waterfowl. Waterfowl depredations do occur i n cert a i n i s o l a t e d l o c a l i t i e s about Roseneath. These are characterized by the presence of one or more large potholes i n which duck flocks congregate and then feed i n the surrounding crop land. Such areas might be removed to prevent any serious c o n f l i c t s from a r i s i n g . At the present time waterfowl and a g r i c u l t u r a l pro-ducts are being produced i n r e l a t i v e harmony on the same land unit about Roseneath. Unless large scale drainage practices, droughts or continued land clearings a l t e r the present condi-tions of the pothole habitat on the study area, i t should con-tinue to have the p o t e n t i a l to produce waterfowl at a r e l a -t i v e l y stable rate. However, such harmony may only be tem-porary f o r the immediate and long term influences of a g r i c u l -ture can e a s i l y become detrimental l i m i t i n g f a c t o r s , i f econ-64 oraic pressures warrant any major land-use changes. Predation as a l i m i t i n g f a c t o r Cartwright (1944) has discussed the t h e o r e t i c a l aspects of predation as a s u r v i v a l factor among renesting species. He showed that i t would be sound management to destroy at least 50$ of the Sharp-tailed Grouse and Hungarian Partridge nests so that a disaster from weather would not wipe out the entire hatch at one time. He sa i d that "Nature uses the predator and other means to stagger the nesting." Errington (1946) has mini-mized the e f f e c t s of predation on s u r v i v a l of adults, f o r an increased predation i s l a r g e l y compensated by reduced mortality from other factors. The e f f e c t of the predator i n l i m i t i n g the breeding potential of waterfowl pairs at Roseneath i s not ob-vious at the present moment. The loss of nests due to predator action has been discussed previously under Table XIII. During 1952 and 1953, 31.8$ and 30.4$ respectively, of the dabbler nests were destroyed by predators and 6.5$ and 6.6$ respectively, of the diver nests were also destroyed by predators. This loss was d i s t r i b u t e d through the nesting season with a higher loss of f i r s t nests recorded. This higher nest loss i n i n i t i a l attempts has been shown also by Kalmbach (1938) at the Lower Souris Refuge. Cartwright (1952) has assumed that a l l females l o s i n g f i r s t clutches of eggs w i l l renest again and s t i l l pro-duce young before the season i s through. With t h i s assumption he uses the figures of Kalmbach (1937, 1938) and a r r i v e s at a f i n a l figure of 80$ successful females and 92$ successful f e -males even though predator loss was 53.5$ and 56.8$ respec-t i v e l y . However, so f a r as waterfowl are concerned Sowls (1951) has shown that renesting may be at a low l e v e l . I f t h i s be general the "Cartwright e f f e c t " w i l l be l a r g e l y l o s t on t h i s group of birds. Predator loss of nests, c h i e f l y to crow, skunk, and ground s q u i r r e l , i s the primary one on the study area (Graphs IV and V) even though the cumulative percentage loss of a l l other factors equals i t . I f , as shown i n Table IX, not a l l pairs are successful i n producing broods, then c e r t a i n l y we must examine the nest losses with more care. The loss of nests to predators, c h i e f l y those of upland nesting species, appears to be at such a magnitude as to a c t u a l l y have some bearing on f i n a l production. However, again only crude hypotheses can be set forward f o r data proving or disproving the r o l e of preda-ti o n i n f i n a l production, are lacking. Our knowledge of yearly renesting percentages i s inadequate. We do not know i f yearly changes i n habitat are r e f l e c t e d i n number of females renesting. The r o l e of weather during the nesting season i s not c l e a r . I f we examine our data i n the l i g h t of present know-ledge a l l we can conclude i s that predators do take nests and also a small percentage of nesting females but t h e i r e f f e c t on end production of any area has not been fathomed. It strongly appears that predation i s accounting f o r the drop i n e f f i c i e n c y and productivity f o r i t i s continually present through the season while most of the other factors act only for a short period of time. Yet, our present data can not 66 be drawn upon for any conclusive evidences. Available t e r r i t o r y - Spat i a l requirements of pairs as a l i m i t i n g factor The work of Hochbaum (1944) has emphasized the role of t e r r i t o r y i n the breeding cycle of waterfowl. He has shown how a drake of a pa i r protects a certain area from a l l other pairs and drakes of h i s own species. From t h i s study waterfowl work-ers have refl e c t e d upon the concept of carrying capacity on the waterfowl breeding grounds. (Stoudt, 1952). The question asked "Can only a cer t a i n number of pairs u t i l i z e a given area because of the s p a t i a l requirement of each p a i r ? " The pothole region gives untold opportunity to study t h i s concept of carrying capacity. From outward appearances t h i s capacity seems to have been reached f o r yearly waterfowl populations do not fluctuate markedly. However, one should not draw con-clusions merely on the basis of census figures when these figures may not be accurate. A phase of the work at Roseneath was an extensive study of breeding pairs and t h e i r r e l a t i o n -ships to the potholes and to the land. The work i s f a r from complete and only some of the r e s u l t s are presented i n the following paragraphs. The concepts of "home range" and t e r r i t o r y i n mammals and birds have received much attention i n the past and are receiving more consideration at the present time. Nice (1941) has compiled an excellent account of t e r r i t o r i a l behaviour i n birds and gives an elaborate summary of concepts up to that time. Howard (1920) had e a r l i e r described t e r r i t o r i a l behaviour 67 i n many bi r d species. Noble (1939) has perhaps given the es-sence of a l l previous works when he defined t e r r i t o r y as "any defended area." The home range concept has not been thoroughly pursued i n the bi r d f i e l d although mammalion workers have writ-ten profusely on i t . Burt (1953) has discussed the home range concept and i t s implications on t e r r i t o r y . Seton (1909) used home range i n h i s work on mammals and explained i t as follows: "No wild animal roams at random over the country: each has a home region, even i f i t has not an actual home." He further stated: "In the idea of a home region i s the germ of t e r r i -t o r i a l thought." Burt (loc. c i t . ) defines the home range as "that area, traversed by the i n d i v i d u a l i n i t s normal a c t i v i t i e s of food gathering, mating, and caring f o r young. . . . T e r r i -tory i s the protected part of the home range, be i t the entire home range or only the nest." The above d e f i n i t i o n s might well apply to the home ranges and t e r r i t o r i e s of most of the spe-cies of waterfowl found at Roseneath. Sowls (1951), working on some surface feeding ducks at Delta, Manitoba, defined home range as "the area i n which a bird spends i t s period of i s o l a t i o n between the break-up of spring gregariousness, following spring a r r i v a l , and the re-formation of f a l l gregariousness." He further noted there was evidence that several favored areas may be used i n any t e r r i -tory and that drakes "defend" from more than one area. De-f i n i t e boundaries of favored areas do not always e x i s t , as previously thought by waterfowl workers (see Hochbaum 1944). Similar observations were noted at Roseneath where the male 68 of a species might show aggressive behaviour, at a l o a f i n g pot-hole or feeding area. E a r l y i n the breeding season the drake may be aggressive at nearly any water area within the home range. As Sowls (loc. c i t . ) speaking of a shoveller pair, points out, "Defensive behavior of her drake did not appear to be the defense of a p a r t i c u l a r piece of ground but rather an attitude that accompanied the p a i r wherever i t moved within i t s home range. 1 1 During the two-year study some attempt was made to gather information pertaining to the water area requirements of breeding p a i r s of ducks. This l e d to an adoption of the home range concept to describe the t o t a l area u t i l i z e d by birds i n t h e i r early seasonal a c t i v i t i e s during the breeding period. The t e r r i t o r y was thought of as the protected part of t h i s home range. The home range included any non-protected spot l i k e nesting area, the feeding spot, or l o a f i n g area. I f the feeding area or l o a f i n g spot was defended by the male, then i t too was included i n the t e r r i t o r y . Although no intensive study was made of the t e r r i t o r i a l and home range concepts, cert a i n neck-banded i n d i v i d u a l s and other ducks with peculiar plumage c h a r a c t e r i s t i c s were followed through part of the breeding season. Enough observations were made on ten i n d i v i -dual ducks i n order that some home ranges might be plotted. Plates I I I , IV, and V show some home ranges plotted f o r the mallard, blue-winged t e a l and canvasback, respectively. A l l of the mallard ranges shown are plotted f o r marked nest-trapped females and perhaps show a r e s t r i c t e d area of use about Plate I I I Mallard Home Ranges ROSENEATH STUDY AREA 0 Adapted from R.C.A.F. Air-Photos: A I I 7 3 0 - 69 A H 6 I 7 - III ® CP potSoles w i t h i n the Home Range ( A l l Females) Potholes with open water Potholes without open water Flooded RFRA. Dugouts ^ P.FR.A. Dugouts Alex Dzubin - 1953 **'*nuHtHH Railroad — Reads m „ Buildings X X points at X which birds observed. Plate IV Blue-winged Teal Home Ranges R O S E N E ^ T J ^ ^ J [ y ^ R E A Minnedosa , Man i toDa Adapted from R.C.A.F. Air-Photos: AII730- 69 AH6I7 - III Potholes with open water Potholes without open water Flooded RFR A. Dugouts ^ P.FR.A. Dugouts Alex Dzubin - 1953 M i n i n m i f H Railroad Roads 2- ^ iPotholes include* in the Home Rang ^ * Points at which birds observed 2, ^  ^Female Home Buildings Ranges 3 P a i r Home Ranges Plate V Potholes U t i l i z e d by Canvasback R O S E N E A ^ M i n n e d o s a , M a n i t o b a Adapted from R.C.A.F Air-Photos: AII730- 69 A 11617 - II Range of Canvasback as governed by water area placement Potholes with open water Potholes without open water Hooded PFR A. Dugouts ^ P.FR.A. Dugouts Alex Dzubin - 1953 '""umtf fH Railroad Roads Buildings Secondary used potholes Primary used potholes Potholes with nests 69 the nest. I f the female was noted on any pothole, t h i s area was included i n the home range. The straight l i n e s j o i n i n g a l l potholes on which the female was observed are perhaps erroneous i n that a l l the area between potholes was not used. Mallard range number 3 was a female which was marked but deserted her nest. She remained on the area f o r some s i x -teen days a f t e r deserting and her range during t h i s time ex-tended eastward of the o r i g i n a l nesting s i t e . Mallard range number 5 was a female which renested a f t e r being nest trapped. Her range i s probably more extensive than a female with but a single nest. The three remaining ranges, 1, 2, and 4 constitute ranges of females trapped during the early part of incubation and show merely the range of the females during that time. A l l of these three ranges extended f o r less than 100 acres. Male ranges were not determined but from an observation of unmarked mallard drakes t h e i r range i s more extensive than females. I t may cover as much as a section of land during the l a s t part of incubation. The p a i r range during the egg laying period does not appear to be over one-quarter of a section. However, as incubation progresses, the drake seems to wander further and further away from the o r i g i n a l protected area and may only r e -turn during the l a t e evening and early morning hours to feed with the hen. During t h i s same time, i . e . , incubation, the mated drake tolerates the presence of other males of h i s spe-cies on his home range. The same mated drake may accompany other drakes over the pothole habitat while they feed i n gre-70 garious groups. However, with the presence of a female, aggressive behaviour does occur on the part of the unmated duck when "he" attacks the female. Benson (1948) mentions that two t e r r i t o r i a l mallard drakes on one pond associated with each other u n t i l one of the females returned and then the assumed mate of the female would attack the other drake. This behaviour was noted only once i n mallards, although i n t r a -s p e c i f i c s t r i f e between blue-winged t e a l , shoveller, gadwall and baldpate drakes was quite pronounced. In mallards t e r r i -t o r i a l defense appeared to take place when a drake attacked the female of the foreign p a i r . The mate of the attacked f e -male remained passive while the t e r r i t o r i a l drake chased his hen, ( i . e . , mate of the attacked female remained about 5 to 10 feet behind the twisting, turning p a i r f l y i n g ahead of him). Mated mallard drakes would, at times, attack other mallard drakes when they flew onto the "waiting" area. The distance that pairs were chased or followed by a t e r r i t o r i a l drake varied markedly. Some mated drakes would follow a p a i r f o r only 50 yards from a pothole edge while others would follow the hen f o r 1500 yards. Plate TV shows the home ranges of two pairs and three female blue-winged t e a l . Blue-winged t e a l ranges 1 and 3 are p a i r ranges and are somewhat larger than the remainder which include only the females. This i s due to the wider range of the drake e s p e c i a l l y during early and l a t e incubation. Female blue-wing ranges, as i n the mallard, appear to be r e -t r i c t e d to a few water areas about the nesting s i t e . Data 71 from unmarked blue-winged t e a l make i t appear that the drake home range i s approximately one-quarter section (160 acres). Female home ranges are much smaller. The nesting s i t e need not necessarily be i n the center of the female home range nor need i t be near any water area most frequented by the p a i r or the female. Females may be seen up to one-half mile from t h e i r nests. Cectain water areas within the home range appear to be more preferred as feeding, l o a f i n g or preening areas than other s i m i l a r appearing potholes. The range i t s e l f can be and i s u t i l i z e d by other pairs as part of t h e i r home range also. Overlapping of ranges i s extensive. Pairs u t i l i z e pot-holes on t h e i r ranges which are not at the time occupied by another p a i r of the same species or may even occupy the same pothole as another p a i r f o r feeding or r e s t i n g . Groups of blue-winged t e a l pairs seem to c l u s t e r about several water areas and form a "community of p a i r s . " I n t r a s p e c i f i c s t r i f e between drakes i s profound but t h i s s t r i f e seems to act only as a stimulating pastime where excess energy i s expended. Drakes show aggressive behaviour f o r an hour or more and then may s e t t l e down and show no aggressiveness f o r an hour. Again f i g h t i n g may occur at some l a t e r time. The presence of the female on the protected area enhances the aggressive response of the male. The actual protected areas of a group of pairs on any one or series of potholes might be very small, as l i t t l e as 40 square f e e t , and vary with the time of day but not exces-s i v e l y from day to day. Also the pothole or series of potholes chosen by the "community of p a i r s " varies from year to year. 72 One 12-acre pothole, which supported three t e r r i t o r i a l pairs i n 1952, did not have any i n 1953. Another series of 5 small pot-holes around a larger area that supported only 1 p a i r i n 1952 had s i x pairs congregated there i n 1953. The presence of one or two pairs on any one area appears, at times, to draw other pairs into the immediate v i c i n i t y . Perhaps the t e r r i t o r i a l f i g h t i n g a c t u a l l y stimulates blue-winged t e a l pairs to s e t t l e and remain near another p a i r ! 1 Plate V shows some of the potholes u t i l i z e d by canvas-backs during the breeding season. Potholes have been divided into primary potholes or "Focal areas," secondary potholes, and nesting potholes. Nesting potholes may, however, be either one of the two aforementioned types or any other permanent or semi-permanent area. No canvasback drakes or females have been marked. However, from observations of d a i l y movements and pot-hole use by t h i s species some idea of the home range has been obtained. "Focal areas" are those potholes where canvasback drakes and pairs were constantly seen during May and June, Here the drakes appear to await the return of the hens from the nesting s i t e . Four such potholes were c l a s s i f i e d as f o c a l areas on the four-section study block, (1 square mile plus is mile buffer zone). Secondary potholes were those areas which were also u t i l i z e d by canvasback pairs but to a l e s s e r extent than primary areas. Drakes did not congregate to any marked degree on these secondary potholes while they did on the f o c a l areas. Both terms are quite subjective but an evaluation of both types of 73 areas could be determined with more intensive work. Nesting potholes were spread over the entire block but females returned regularly to the f o c a l areas. The two most southern primary potholes show a number of nests i n the smaller potholes about them. (Plate VT). The northern two show thi s to a l e s s e r ex-tent. Nests also appeared i n potholes some distance away from these f o c a l areas. Here the drake might be found i n a large water area adjacent to the nesting pothole. The acreages of the four f o c a l areas were 11.9, 3.4, 3.5, and 4.8 acres. Each area except the 11.9 acre pothole had a maximum depth of at least 8 feet or more, which was decidedly deeper than the usual 2 - 5 foot range found i n most permanent areas. The two most southern f o c a l areas also contained large quantities of fresh water shrimp, Gammarus, which was not common to more than s i x permanent areas over the four-square mile block. Per-haps food was a f a c t o r i n the choice of these areas as con-gregating points. However, canvasback were seen to feed i n other potholes. A comprehensive stomach analysis investiga-t i o n plus an intensive study of pothole limnology would un-doubtedly show why c e r t a i n potholes are u t i l i z e d f o r feeding and others are not. Nine of the 51 canvasback nests found, during the two year period, were i n C or temporary potholes while 42 were i n B or semi-permanent water areas. The sizes of the various potholes chosen f o r nesting by canvasbacks are given i n Table XIV. TABLE XIV Size of Potholes used by Canvasback f o r Nesting and Frequency of Nests i n Each Size Size i n Acres Number of Nests .01 - .19 -.2 - .39 10 .4 - .59 6 .6 - .59 3 .8 - .99 2 1.0 -1.49 8 1.5 -1.99 4 2.0 -2.49 1 2.5 -2.99 3 3.0 -5.99 8 6.0 -8.99 3 9.0 -12.0 3 Although the two year study has not substantiated any new facts regarding t e r r i t o r i a l i t y and home range i n water-fowl, c e r t a i n tentative g e n e r a l i t i e s might be set f o r t h . These are merely from a series of observation on marked and unmarked i n d i v i d u a l s . As our knowledge increases these gener-a l i t i e s too, might change. They are recorded here only i n an attempt to show the author fs inte r p r e t a t i o n of observed be-haviour and to stimulate other opinions or further work on the subject. 75 1. The home range of waterfowl has previously been described by Sowls (1951). Burt's (1943) descrip-tion of home range i n mammals as, "that area t r a -versed by the i n d i v i d u a l i n i t s normal a c t i v i t y of food gathering, mating, and caring f o r young ... T e r r i t o r y i s the protected part of the home range, be i t the entire home range or only the nest" can also apply to waterfowl as found i n a portion of the pothole region. 2. The siz e of the home range varies between species and also between individuals of the same species. 3. The si z e of the home range of each sex varies, the drake having the larger home range. The home range of the female may be very small during incubation. 4. Population density might also influence s i z e of the home range. The pressure exerted by surrounding pairs might contract the home range to conform more cl o s e l y to the t e r r i t o r y . 5. Home ranges of d i f f e r e n t pairs overlap. The water areas used by one pai r depends at times on the pre-sence or absence of other p a i r s , of the same spe-c i e s , on these water areas. 6. Home range varies with topography of the land and the r e l a t i o n of potholes to one another. I f the da i l y and seasonal requirements, i n terms of food, nesting cover, and l o a f i n g areas are found i n a few adjacent areas, then the range w i l l be smaller. The placement of the nest and the feeding area to 76 the "waiting area of the drake governs size of the range. Infrequent random movements of p a i r s , males or females, should not be included i n the home range. 7. The t e r r i t o r y or protected area may include the feed-ing area, l o a f i n g spot, or i n some divers even the nesting area. The female, during egg laying and early part of incubation, joins the drake on some water area which i s termed the waiting area of the drake. This water area i s protected from a l l other pairs of the species and i n most cases from other mated drakes. Aggressiveness of males loses i t s i n -tensity as incubation advances. 8. Aggressiveness of males i s enhanced by the presence of t h e i r own mate. The t e r r i t o r i a l drake usually attacks the female of a foreign p a i r . In the mallard and p i n t a i l the drake of a foreign p a i r remains pas-s i v e l y f l y i n g behind during the time his female i s being chased by a t e r r i t o r i a l drake. In the sho-v e l l e r , baldpate, gadwall, blue-wing and green-wing t e a l , both males do f i g h t i n midair during t e r r i t o r -i a l defense. In canvasback, the male protects only a small portion about the female and t h i s protected area moves as the female does. The drake attacks males or females which swim near. No actual t e r r i -t o r i a l protection of some water area has been seen i n the canvasback. However, the male may show ag-gressiveness to other p a i r s , i f they are near a 77 nesting canvasback female. 9. T e r r i t o r i a l defense i n the blue-wing t e a l does not seem to be to the same degree of severity throughout the day, i . e . , drakes may attack each other f o r an hour and then remain passive f o r an hour. Aggres-siveness may be sporadic and not always of the same i n t e n s i t y . Certain blue-wing drakes continually attack other drakes, often f l y i n g several hundred yards to other potholes. In these cases f i g h t i n g seems to be merely a stimulating act where drakes expend t h e i r excess energies. However, aggressive-ness does take place very often but i t s function tends to be complex. It may serve to: (a) Separate one p a i r of ducks from a l l other pairs of that species and ensure the s p a t i a l require-ment of these birds f o r breeding purposes. (b) Protect the female only, from other drakes. Many cases, where a female has been forced down onto a pothole and "raped n by a drake other than her own have been recorded. (c) Necessarily stimulate other breeding birds, i . e . , one pa i r of birds by i t s presence and ag-gressiveness stimulates another p a i r to breed and nest i n close proximity. 10. In the l a s t analysis, one might conclude that there i s a d e f i n i t e aggressiveness, i n the waterfowl spe-cies using the potholes about Roseneath, which varies 78 i n i t s i n t e n s i t y i n the various species of water-fowl and also between individuals of the same spe-c i e s . The t e r r i t o r y or protected area may vary through the day and from day to day. There are no strong and f a s t rules which might apply to s i z e , shape, requirements and function of t e r r i t o r y . These change as the season progresses and appear to change as the breeding habitat does. The obser-vation have only shown how l i t t l e i s a c t u a l l y known of t e r r i t o r i a l i t y of waterfowl i n the pothole habi-tat and the part i t plays i n a c t u a l l y l i m i t i n g a ce r t a i n number of one species to breed on a given area. They further show that our previous con-cepts may have to be re-examined under l i g h t of present data and draw attention to the f a c t that more intensive future studies are needed. DISCUSSION The two year study has determined the yearly production and some of the breeding biology of a number of waterfowl pairs u t i l i z i n g a small part of the pothole-agricultural region of Manitoba. A description of the more prominent, po t e n t i a l l i m i t -ing factors has been made and several hypotheses advanced as to how these environmental pressures might govern f i n a l production. Evans et a l (1952) have previously noted that the present high productivity of the area i s due to i t s climate, physio-graphy, d i v e r s i f i e d land use, and an interspersion of pothole 79 types. They have assessed the waterfowl habitat of t h i s region and recorded various management suggestions. They note that each pothole has a di f f e r e n t use during the breeding and brood seasons. The present study more than emphasizes the concept of a community re l a t i o n s h i p of potholes wherein one series of water areas i s used i n the breeding and nesting season, while another, perhaps d i f f e r e n t , series i s u t i l i z e d during the brood period. The d a i l y and seasonal requirements of a pa i r of ducks i s characterized and found i n a whole group of var-ious water areas, each one having some one or more functions. No ^ one pothole seems to completely f i l l the seasonal need of any breeding pair i n terms of l o a f i n g spot, feeding, area, nesting area, t e r r i t o r y and brood pothole. Pairs need "space" even though t h e i r above requirements might be found i n sev-e r a l adjoining potholes. This s p a t i a l requirement of water-fowl seems to be psychological i n nature and without a more intense study of breeding behaviour our knowledge of t h e i r requirements w i l l never be c l e a r l y understood. Even the com-p l e x i t y of the "normal" breeding season, with i t s pairs each i n a d i f f e r e n t phase of the breeding cycle, w i l l have to be unravelled before the i n t e r - r e l a t i o n s h i p of pairs and the land i s appreciated. Each pothole, although having a ce r t a i n breeding use value, i s needed f o r a short period of time i n the spring simply as a unit of re t r e a t . When pairs make themselves f o r -eign to each other by aggressive behaviour and these realms of aggressiveness are very large excess space i s needed by other pairs i n order to remain out of these protected areas. I f the space i s not available perhaps c e r t a i n pairs are thwarted from s e t t l i n g i n c e r t a i n water areas. Even though one pothole may be u t i l i z e d only f o r a few short days i n the spring, i t s occurrence therein has assured that another p a i r remains on the given breeding unit . Such may well be the use valve of the many transient ponds i n the spring. Certainly, excess areas seem to be present i n the spring. The populations of the two years were quite s i m i -l a r even though there was a marked reduction i n the a v a i l a -b i l i t y of small water areas i n 1952. How these areas a c t u a l l y f i t i nto the waterfowl use patterns i s not known. The present "stable" breeding populations may be the r e s u l t of a number of environmental factors yearly balancing out or may be due to s t a b i l i t y i n the habitat. Perhaps yearly placement and a v a i l a -b i l i t y of nesting cover, of permanent feeding areas or l o a f i n g spots may a l l contribute to thi s population number neither i n -creasing nor decreasing. No di r e c t comparison can be made of the "day use" or "seasonal use" of one pothole without f i r s t describing the cha r a c t e r i s t i c s of the land and other potholes surrounding i t . Different species appear to have d i f f e r e n t requirements so that although one pothole may be excellent f o r the t e r r i t o r y of a mallard, i t cannot serve t h i s function f o r a blue-winged t e a l . S i m i l a r l y brood potholes vary i n s i z e , shape, and depth and c e r t a i n species prefer d e f i n i t e types. The presence of-absence of other ducks of any one species may serve as a factor governing the choice of immediately surrounding potholes by other pairs of t h i s species. Thus, the presence of one p a i r on a "good" pothole influences the choosing of a "secondary 1 1 pothole by another p a i r . I f very few areas occurred and such potholes were of primary importance f o r mallard t e r r i t o r i e s , we could not expect a l l birds to use t h i s one area. However, where only one water area i s available to p a i r s , as i n the short grass p r a i r i e , and t h i s water area must serve a l l purposes, the breed-ing unit must surely change. One notes that perhaps the water areas are not producing ducks at t h e i r maximum capacity; that i s , some " s u p e r f i c i a l " carrying capacity seems to have been reached. Potholes that contained nesting canvasback and t e r r i -t o r i a l blue-wing drakes i n one year often do not contain these birds the following year. Perhaps hunting pressure i s keeping the population at.such a low l e v e l that only the "choicest" areas are u t i l i z e d . Small immeasurable habitat changes may also occur yearly. As a management implication, the concept of the community rel a t i o n s h i p of potholes can be extremely useful. I f any future drainage i s contemplated, managers w i l l have to take into ac-count the r e l a t i o n s h i p of one pothole to the others i n the ser-i e s . The draining of one area not only w i l l destroy that area as f a r as waterfowl use i s concerned, but i t may disrupt the balance between a l l other potholes i n the s e r i e s , destroying not the one area but an entire group. More basic work i s needed i n order to weight.the importance of each water area and the r o l e i t plays i n the breeding unit. Because potholes occur i n an a g r i c u l t u r a l area, future land use w i l l tend to determine whether or not a l l potholes w i l l remain. The long-term changes now i n progress w i l l un-doubtedly influence waterfowl production. No large scale changes are evident but the slow paralyzing changes of land cl e a r i n g are yearly there. A fence l i n e i s plowed under, a corner of a f i e l d i s put to the plow, a small b l u f f i s cleared a l l these land a l t e r a t i o n s w i l l accumulate into a s i g n i f i c a n t interference with waterfowl, yet s i n g l y they might be ignored. Road allowances, fence rows and waste uplands that are now prime nesting cover may a l l disappear.if economic conditions warrant any increase i n a g r i c u l t u r a l a c t i v i t y . Thus waterfowl may be forced to nest i n grain stubble as they do i n the short grass regions of the west. I f t h i s occurs then only those spe cies which can r e a d i l y adapt themselves to the change w i l l f l o u r i s h . The habitat i t s e l f i s continually changing, depressions slowly f i l l , and the small h i l l s erode away; the vegetation i t s e l f a l t e r s . The change of potholes to the c l i m a t i c climax w i l l undoubtedly create a habitat with poor interspersion of pothole types. Yet, because of the presence of agriculture and especially c a t t l e , climax conditions do not often occur. To t h i s extent a g r i c u l t u r a l influence i s b e n e f i c i a l . Water a v a i l a b i l i t y and weather factors appear to be the most important environmental pressures which might tend to l i m i t yearly productivity. And yet, surface water has been lacking only twice during the l a s t half century. Local f a r -mers rel a t e that only two dry periods occurred; one i n 1915, 83 the other i n 1933-35. The climate of the region, governed c h i e f l y by the presence of the Riding mountains to the north, yearly ensures a p l e n t i f u l supply of water f o r the breeding seasons. S u f f i c i e n t winter snows f a l l and l a t e r melt so as to a t t r a c t breeding p a i r s . Then, excess June rains f i l l a l l de-pressions to near capacity, leaving s u f f i c i e n t water f o r broods. This bountiful yearly p r e c i p i t a t i o n does create a pothole habi-tat that can and does yearly supply a good number of ducks into the M i s s i s s i p p i Flyway. The effects of predation on duck production i n the pot-holes cannot be ignored. I t i s a constant and important pres-sure on a l l nesting species. Yet i n r e a l i t y we do not know the true r o l e of predation and i t s determination of f i n a l produc-t i o n . I f i t was removed perhaps other l i m i t i n g factors Would then become important and compensate f o r the losses (Erring-ton, 1946). A quantitative study of the e f f e c t s of the various predators on nest destruction and bird mortality i s needed. Suggestions f o r Management Management often implies that nearly a l l basi£ facts con-cerning a problem are known and the sound manipulation of en-vironmental factors i s taking place i n order to increase pro-duction or better habitat. At the present moment very few of the ecological and behavioral problems of the pothole country are i n a "near-solved w state. The suggestions as presented are only tentative. 84 Certain manipulations of habitat might now be made i n order to see i f by the lack of some factor the maximum produc-tion possible i s not being attained. Creation of more l o a f i n g areas might well increase the p o s s i b i l i t i e s of a higher breed-ing population. Many of the potholes do become choked and over-grown with vegetation and l o a f i n g areas are few i n numbers. I f some program of intensive management of small water areas was put into e f f e c t , then i t might include: A. The spraying of sections of c a t t a i l and whitetop potholes with chemicals to remove a l l vegetation or, B. The building of small l o a f i n g r a f t s as outlined by Sowls (1951) or,C. The management of the muskrat i n order that more houses might be b u i l t and these used f o r l o a f i n g areas. The protection of potholes from grazing as outlined by Evans et a l i n an attempt to improve t h e i r q u a l i t i e s as t e r r i -t o r i a l waters may well be a long term project. The same r e s u l t s might be achieved more r e a d i l y by the use of chemical sprays. Overgrazed potholes were heavily u t i l i z e d by breeding p a i r s , e s p e c i a l l y f o r l o a f i n g spots. Pairs from many surrounding water areas congregated on one area that was nearly denude of vegetation. Small overgrazed areas as usually found near farm buildings are b e n e f i c i a l and although such practices as over-grazing should not be favoured, they should not be condemned on small areas. U n t i l such time as use factors of various potholes are understood, no drainage schemes should be undertaken. Yet, speculation of the probable b e n e f i c i a l e f fects of draining 8 5 several small areas to create a large one, so that s u f f i c i e n t water remains f o r brood development, can be made. I f drought conditions warranted th i s action and potholes were being i n -tensively managed to produce more birds, such drainage schemes might well increase production. A l l suggestions as outlined could only be applied i f the pothole region were being intensely managed. Such manage-ment may well come i n the future but perhaps only at a time when the pothole waterfowl population reaches a low c r i t i c a l l e v e l . 86 ACKNOWLEDGEMENTS There are many people who, at one time or another, have given me t h e i r unselfish a i d and who have helped i n the com-pl e t i o n of this program through donations of time energy and s k i l l . To these people I give my humble and sincere thanks f o r without t h e i r assistance the work would be f a r from f i n -ished. The following people and organizations are commended f o r t h e i r a i d : To the farmers about Roseneath whose help and under-standing made the project possible. My thanks to: H. Brugger, Dave Waebel, E a r l Waebel, Alex Cox, Floyd Calen, E. Wilkinson, C. Meadows, F. Rush, Ken Enquist, and E a r l Enquist. To Mrs. A. Macdonald, Mary, and E f f i e , of Minnedosa, who, f o r three summers, made t h e i r home also mine. To H.A. Hochbaum, di r e c t o r of the Delta Waterfowl Research Station, f o r his continued a i d and h i s appreciation of f i e l d problems, and also f o r his help i n the preparation of the manuscript. Mr. Hochbaum made cer t a i n that budgets were complete, l i v i n g quarters kept i n order and extra labor made av a i l a b l e , when needed. To Dr. I. McT. Cowan, Head, Department of Zoology, University of B r i t i s h Columbia, f o r his help i n i n i t i a t i n g the project, f o r his continued inter e s t i n the work, and f o r his a i d i n the completion of the manuscript. To Dr. W.A. Clemens, former Head, Department of Zoology, f o r his u n f a i l i n g a i d during my f i n a l two years i n the department. 87 To the W i l d l i f e Management I n s t i t u t e , Washington, D i s t r i c t of Columbia, f o r t h e i r monetary a i d during the past three years. To Mr. C. R. Gutermuth, of the I n s t i t u t e f o r his support of my yearly budget. To the National Research Council of Canada, who made possible the purchase of needed summer equipment and also gave me the opportunity to continue my university work, during the winters, by graciously granting a bursary and a scholarship f o r t h i s purpose. To my Mother and Father whose f i n a n c i a l and other a i d w i l l always be remembered. I also wish to express my sincere appreciation to the Manitoba Game and F i s h e r i e s Branch, e s p e c i a l l y to Mr. G.W. Malaher, the d i r e c t o r , f o r making available a Nissett Hut f o r the duration of the study. Also f o r the assistants placed at my disposal. Mr. Stan Kolt gave invaluable assistance during May of 1952. My appreciation to the members of the United States F i s h and W i l d l i f e Service, e s p e c i a l l y of Region I I I , Minnea-p o l i s , f o r t h e i r continued co-operation. Other people who gave f r e e l y of t h e i r time and knowledge are l i s t e d below. My appreciation to: Mr. William K i e l , University of Wisconsin, f o r helping me to remain i n waterfowl work, f o r his kind understanding of my problems, and f o r his aid i n my f i e l d work. Arthur S. Hawkins, F i s h and W i l d l i f e Service, f o r his continued i n t e r e s t i n the project and f o r his help i n solving various f i e l d problems. 8 8 Edward G. Wellein, Pish and W i l d l i f e Service, whose aid and understanding during my f i r s t summer at Delta gave me a clearer insight into some of the problems of waterfowl management. Bernard Gollop, Canadian W i l d l i f e Service, who c r i t i -c a l l y read and corrected the f i r s t draft and gave many v a l -uable suggestions. Drs. R.A. McCabe and J . J . Hickey, University of Wis-consin, f o r t h e i r h e l p f u l suggestions. Peter Ward and Nan Mulder of Delta f o r t h e i r continued help on the project. Graduate students at Delta f o r t h e i r f i e l d a i d , es-p e c i a l l y Milton Weller, Ted D i l l o n , George Brakhage, Ron Bal-ham, and Tom Bergervd. Also to Bob Klopman who spent a month, during 1953, at Roseneath helping to trap birds and l a t e r to photograph them. U.S. Game Management Agents, Wes Newcomb, Jerry Pospichal, Don Krieble, and Rex Tice f o r t h e i r a id i n censusing and trapp-ing birds. I wish also to thank many others, too numerous to men-t i o n , who have helped me i n the course of the study. * * * 89 LITERATURE CITED Bach, Roy N. 1951 Some aspects of North Dakota's surface water. (Unpublished) N.D. Game and Pish Department, Bismarck, N.D. Di v i s i o n of Federal Aid. Bennett, L.J. 1937 Grazing i n r e l a t i o n to the nesting of the blue-wing t e a l . Trans, of the 2nd N.A.W.C.: 393-397. 1938a The blue-winged t e a l , i t s ecology and management. Ames, Iowa. Collegiate Press Inc. : 1-144. 1938b Redheads and ruddy ducks nesting i n Iowa. Trans-action of the 3rd North American W i l d l i f e Con-ference: 647-650. Benson, Robert D. 1948 Basic factors determining the waterfowl production on three p r a i r i e ponds i n 1947. Master of Science Thesis, University of Minnesota. Bird, R.D. 1930 B i o t i c communities of the aspen park land of Central Canada. Ecology 11 (2): 365-442. Black, K. and CD. Evans 1953 In Improvements to the Cannon Net Trap. U.S. Fish and W i l d l i f e Service. Branch of W i l d l i f e Refuges. W i l d l i f e Management Series No. 12. 25 pp. Blankenship, Lyt l e H. 1952 Use of duckling ages f o r studies of waterfowl popu-l a t i o n s and production on p r a i r i e stock ponds i n western South Dakota. Master of Science Thesis, University of Minnesota. Bue, I.G., Ly t l e Blankenship and W.H. Marshall 1952 The re l a t i o n s h i p of grazing practices to waterfowl breeding populations and production i n Western South Dakota. Trans, of the 17th N.A.W.C.: 396-414. 90 Burt, William Henry 1943 T e r r i t o r i a l i t y and Home Range concepts as applied to mammals. Journ. Ham. 24: 346-352. Cartwright, B.W. 1948 The western Canadian waterfowl breeding grounds. Transaction of the 13th North American W i l d l i f e Conference: 63-68. 1952 A comparison of potential with actual waterfowl production. Transactions of the 17th North Ameri-can W i l d l i f e Conference: 131-138. C o l l s , D.G. 1951 The c o n f l i c t between waterfowl and agr i c u l t u r e . Trans, of the 16th N.A.W.C.: 89-93. Connor, A.J. 1939 The Climate of Manitoba. Economic Survey Board. Province of Manitoba, 1939, 1-163 pp. Cowan, I. McT., and James Hatter 1949 Waterfowl breeding ground survey i n B r i t i s h Colum-bi a , 1949. In: Waterfowl populations and breeding conditions. Summer 1949. With notes on woodcock and wilson snipe. U.S.D.I. and Canada Department of Mines and Resources, Special S c i e n t i f i c Report, W i l d l i f e No. 2: 24-29. Crissey, Walter F., and others. 1949 Waterfowl populations and breeding conditions -Summer, 1949, with notes on woodcock and wilson snipe. Special S c i e n t i f i c Report: W i l d l i f e No. 2. Dashinske, R.L. 1953 Drainage and Subsidy Payments Trans, of the 18th N.A.W.C.: 73-80. D i l l , H.H. and W.H. Thornsberry 1950 A cannon-projected net trap f o r capturing waterfowl. Jour. W. Mgt. 14(2): 132-137. Dzubin, A. 1952 In waterfowl populations and breeding conditions, Summer, 1952. Special S c i e n t i f i c Report: W i l d l i f e No. 21: 71-75. U.S. Fish and W i l d l i f e Service and Canadian W i l d l i f e Service 1952. 91 E l l i s , J.H. 1948 The S o i l s of Manitoba. Economic Survey Board. Province of Manitoba, 1938, 1-112 pp. Errington, Paul L. 1942 On the analysis of productivity i n populations of higher vertebrates. Jour. W i l d l i f e Mgt. 6: 165-181. Evans, CD. 1949 In waterfowl populations and breeding conditions. Summer 1949. With notes on woodcock and Wilson snipe: 71-75. U.S. F i s h and W i l d l i f e Service and Dominion W i l d l i f e Service 1952. Evans, Charles D. 1951 A study of the movements of waterfowl broods i n Manitoba. Master of Science Thesis, University of Minnesota. Evans, CD., A.S. Hawkins and W.H. Marshall 1952 Movements of Waterfowl broods i n Manitoba. Special S c i e n t i f i c Report: W i l d l i f e No. 16. U.S. F i s h and W i l d l i f e Service 1952. 1-47-XIX plates. Evans, C. and W. Nord 1952 Progress report on pothole drainage (unpublished). River Basin Studies, U.S. Fish and W i l d l i f e Service. Region 3 (In Peterson 1952). Furniss, O.C. 1938 The 1937 waterfowl season i n the Prince Albert d i s -t r i c t , central Saskatchewan. Wilson B u l l . 50: 17-27. Gavin, Angus 1953 Agriculture reaches northward i n Canada. Transact-ions of the 18th North American W i l d l i f e Conference: 118-121. Guhl, A.M. and L.L. Ortmann 1953 V i s u a l patterns i n the recognition of i n d i v i d u a l s among chickens. Condor 55: 287-298. 92 Harrisson, J.D.B. 1934 The Forests of Manitoba. Department of I n t e r i o r Publication. Ottawa 1934. 1-80 pp. 1937 A Forest C l a s s i f i c a t i o n of Canada, Dominion Depart-ment of Forestry, Ottawa. Hochbaum, H. Albert 1944 The canvasback on a p r a i r i e marsh. American Wild-l i f e I n s t i t u t e , Washington, D.C. 201 pp., i l l u s . 1946 Recovery potentials i n North American waterfowl. Transactions of the 11th North American W i l d l i f e Conference! 403-415. 1947a Where are the Ducks? Wisconsin Cons. B u l l . 12 (9): 13-14. 1947b The marshes need more ducks. Outdoor L i f e . Sept-ember 1947. Howard, H.E. 1920 T e r r i t o r y i n Bird L i f e . Murray, London, 308 pp. Kalmbach, E.R. 1937 Crow-waterfowl r e l a t i o n s . U.S. Department Agr., C i r c u l a r 443. 1938 A comparative study of nesting waterfowl on the Lower Souris refuge: 1936-1937. Transactions of the 3rd North American W i l d l i f e Conference: 610-23. 1939 Nesting success: i t s s i g n i f i c a n c e i n waterfowl reproduction. Transactions of the 4th North Amer-ican W i l d l i f e Conference: 591-604. K i e l , W.H. In waterfowl populations and breeding conditions, Summer, 1952. Special S c i e n t i f i c Report: W i l d l i f e 1952 No. 21: 66-70. U.S. Fish and W i l d l i f e Service and Canadian W i l d l i f e Service, 952. Kimball, J.W. 1953 Wise land use w i l l save the potholes. Address 15th Midwest W i l d l i f e Conference. Leit c h , W.G. 1951 Saving, maintaining and developing waterfowl habitat i n western Canada. Trans, of the 16th N.A.W.C.: 94-99. 93 Leopold, Aldo. 1933 Game Management. Chas. Scribner*s & Sons, New York. Low, Jessup B. 1945 Ecology and management of the redhead (Nyroca  americana) i n Iowa. Ec o l . Monog., 15: 35-69. 1940 Production of the redhead (Nyroca americana) i n Iowa. Wilson B u l l . 52(3): 153-164. Mair, W. Winston 1953 Ducks and Grain. Transactions of the 18th North American W i l d l i f e Conference: 111-117. M i l l e r , A.W. and B.D. C o l l i n s 1954 A nesting study of ducks and coots on Tule Lake and Lower Klamoth National W i l d l i f e Refuge. C a l i f . F i s h and Game 40 (1): 17-37. Nice, M.M. 1941 The r o l e of t e r r i t o r y i n bi r d l i f e . Am. Midi. Nat. 26 (3): 441-487. Noble, G.K. 1939 The r o l e of dominance i n the l i f e of bi r d s . Auk 56 (3): 263-273. Peterson, Elmer 1952 Marsh drainage and waterfowl. Trans, of the 17th N.A.W.C.: 123-131. Ramsay, A.O. 1951 F a m i l i a l Recognition i n Domestic Birds. Auk 68 (1): 1-16. Schoenfeld, Clay 1949 Good-bye pot-holes. F i e l d and Stream, V o l . 58 (12). Schrader, Thomas A. 1949 Recent w i l d l i f e developments i n r i v e r basin manage-ment. Address 11th Midwest W i l d l i f e Conference. 94 Seton, B.T. 1909 L i f e - h i s t o r i e s of northern animals. An account of the mammals of Manitoba. New York, Charles Scribner*s Sons, Vol. 1 & 2, 1267 pp. Shortt, J.M. and Sam Waller 1937 The birds of the Lake St. Martin Region, Manitoba. Contrib. Roy. Ont. Mus. Zool. No. 10, 51 pp. Soper, J.D. 1948 Canada looks at waterfowl. Transactions of the 13th North American W i l d l i f e Conference: 52-56. Sowis, Lyle K. 1950 Techniques f o r waterfowl nesting studies. Transac-tions of the 15th North American W i l d l i f e Confer-ence: 478-487. 1951 A study of the ecology and behaviour of some sur-face-feeding ducks. Ph.D. Thesis, University of Wisconsin. Stoudt, Jerome H. 1940 A waterfowl census technique and i t s ap p l i c a t i o n on the Chippewa National Forest. Master of Science Thesis, University of Minnesota. 1952 In waterfowl populations and breeding conditions, Summer, 1952. Special S c i e n t i f i c Report: W i l d l i f e No. 21: 52-60. U.S. Fish and W i l d l i f e Service and Canadian W i l d l i f e Service, 1952. Smith, Robert H. and Arthur S. Hawkins 1948 Appraising waterfowl breeding populations. Tran-sactions at the 13th North American W i l d l i f e Con-ference: 57-62. Thompson, E.E. 1890 The birds of Manitoba. Proc. U.S. Nat. Mus. Vol. 13, No. 841. pp. 457-643. Williams, C e c i l S., et a l 1948 Waterfowl breeding conditions - Summer, 1947. Special S c i e n t i f i c Report Number 45. 95 Williams, C e c i l S., et a l 1950 Waterfowl populations and breeding conditions G Summer, 1950, with notes on woodcock and wilson snipe. Special S c i e n t i f i c Report: W i l d l i f e No. 8. Yocum, Charles F. 1950 Weather and i t s e f f e c t on Hatching of Waterfowl i n Eastern Washington. Transactions of the 15th North American W i l d l i f e Conference: 309-319. -» * # 

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