UBC Theses and Dissertations
An intensive study of waterfowl populations on a small block of agricultural land, Minnedosa, Manitoba; the breeding, biology and production of some diving and dabbling ducks of the "pothole-agricultural" breeding habitat in south-central Manitoba Dzubin, Alexander
The thesis embodies the results of a two-year study, 1952 and 1953, of the breeding biology and production of some diving and dabbling ducks on the "pothole-agricultural” region of South-Central Manitoba. The study area was a section and a half block of pothole (small slough) country nine miles south of Minnedosa, Manitoba. Its knob and kettle topography was characteristic of the region and its land use, climate, and vegetative cover was typical of the southern aspen parklands. The objectives were to assess the waterfowl habitat, to determine species composition, productivity, reproductive efficiency, and to determine the environmental pressures as they applied to the waterfowl of this habitat. Breeding pairs of birds were trapped, then, color leg banded, painted, or neck banded in order to be followed. Broods were color marked by the injection of dyes into the eggs. Mallards were the most common species breeding here, making up 33.7$ of total composition, blue-winged teal with 23.3%, canvasback with 10.1%; baldpate, pintail, redhead, ruddy duck, shoveller, gadwall, green-winged teal and lesser scaup made up the remainder. Populations of birds rose to peak figures during the first week in May. Blue-wings arrived much later than canvasback or mallard. Newly hatched broods were seen from May 23 to August 8 in 1952 and from June 2 to August 23 in 1953. 94.1 breeding pairs of birds in 1952 and 90.8 pairs in 1953 produced 49.4 and 60.2 broods respectively. Efficiency (brood/pair ratio) of dabblers varied from .28 for pintails to .85 for blue-wings. Mallard efficiency was .37 and .51 for the two years. Diver brood/pair ratio was higher than dabblers. The area of 1 square mile produced 331 young in 1952 and 355 in 1953. Average maximum brood size for all species and all age classes was 6.9. Reduction in brood size with increase in age was noted; Class I broods averaged 7.1, Class II - 6.8, Class III - 6.4. Nesting studies indicated that cattail was the chief nesting cover followed by upland grasses, whitetop, bulrush, annual weeds, and others. 52.6% of all 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 bluffs, willow rimmed potholes, and stubble fields. All divers nested in the emergents in potholes. 43.9% of all dabbler nests in 1952 and 37.2% in 1953 hatched successfully. Diver hatching success was higher, 67.7% in 1952 and 64.5% in 1953. Predator losses were 31.8% and 30.4% for dabblers but only 6.5% and 6.6$ for divers. Desertion and Intolerance, agricultural activities, flooding, freezing weather and dye loss accounted for the rest. Brood hatching periods appeared to be later in 1953. Weather plays an important role in making available surface waters for breeding pairs and broods. Secondarily it influences nest hatching success. More dry potholes were recorded, at comparable times in 1952 than in 1953. Pothole water levels were all higher in 1953. Agricultural practices influence waterfowl production either immediately, through a destruction of nests and cover or through long term influences by encroachment on cover and conversion of waste uplands and potholes into crop lands. There is danger of future drainage in the region with subsequent loss of habitat. Predation was the chief cause of most of the nest destruction and undoubtedly had a marked effect on final production. The spatial requirements of breeding pairs is not clear. Blue-wing home ranges covered one-quarter of a section, mallards - one section, and canvasback -four sections. Aggressiveness varied in individual pairs from time of day and from day to day. Management suggestions for the region included the creation of more loafing spots, through chemical treatment of vegetation or through a building of small rafts. Management practices only apply if the pothole water areas are to be managed intensively. The concept of the community relationship of potholes will have to be taken into account before any future drainage is contemplated.