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Advantages to late breeding in Ruddy ducks Somerville, Alison Joan 1985

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ADVANTAGES IN  TO  LATE  RUDDY  BREEDING  DUCKS  by ALISON  JOAN  SOMERVILLE  B.Sc . ( H o n s . ) , U . B . C ,  Vancouver,  1981  A THESIS THE  SUBMITTED IN P A R T I A L F U L F I L L M E N T R E Q U I R E M E N T S FOR T H E D E G R E E OF MASTER OF S C I E N C E in T H E F A C U L T Y OF GRADUATE S T U D I E S (Department of Zoology)  We  accept  THE  ©  this thesis required  as conforming standard  U N I V E R S I T Y OF B R I T I S H October 1985  Alison  Joan  t o the  COLUMBIA  Somerville,  OF  1985  In presenting  this thesis in partial fulfilment of the  requirements for an  advanced  degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and  study. I further agree that permission  copying of this thesis for scholarly purposes may department  or  by  his or  her  representatives.  be  permission.  Department of  Zoology  The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date  October 15,  1985  granted by the head of  It is understood  publication of this thesis for financial gain shall not be  for extensive  that  copying  allowed without my  my or  written  i i  ABSTRACT Ruddy nest  in  Ducks  late  waterfowl  This of  Barrow's do  not  and  June,  breeding  able and  abundance  to  to  renest).  southwestern  Ducks  Coot  higher  dive  Ruddy  ducklings  durations  Reduced  These  nests,  of  late  ambient and  more  may  enable  nest  flooding  late  young  in  were  age  to  that  females females  summer  these  of did  not  Ducks  in  mature young  American  before  time ponds  produced  per  Coots.  hatch  successfully  any  Ducks  breeds  to but  early  predation,  of  ducklings,  vegetation  and  not  to  hatched  by  maximize  energy  for  season,  dependence  abundance  pair  Ruddy  young;  this the  Ducks of  almost  however,  food study.  timing  shorter  average  percent  of  of  Columbia.  and  the  whereas  by  British  freeze, of  incubation.  and  explain  renest  nest  resting  greater  do  reduced  during  demonstrated  Forty young,  to the  southwestern  insufficient  not  the  early  include  feeding  in  and  factors apparently  i n Ruddy  class  that  include  ducklings  for  2B  affect  breed  green  other  Columbia,  Ruddy  behavior  of  frequent  for nesting  to  factors  temperature  vegetation  ducklings  species  breeding  green  Despite  may  that  Columbia  most  British  comparing  feeding  on  breeding  (a  than  that  (species  availability  advantages  Longer  Therefore,  by  British  temperature.  and  growth.  of  of  later  factors  American  food,  in  Possible  in  Bufflehead  and  of  predation  and  parklands  e a r l y August,  i n Ruddy  desertion  fluctuations  and  thesis considers  renest)  flooding  Chilcotin  breeding  Goldeneye  is  the  July  species  Canada. timing  in  time  for  number  of  was  similar  nesting a l l nesting  survival  of  Ruddy Coot Ruddy  iii  d u c k l i n g s to 2B age c l a s s of American Coots,  (four weeks old) was  Barrow's Goldeneye and  higher than  Bufflehead.  that  iv  TABLE  OF  CONTENTS  ABSTRACT  i i  LIST  OF T A B L E S  LIST  OF F I G U R E S  v i i ix  ACKNOWLEDGEMENTS  x  CHAPTER  ONE: G e n e r a l  CHAPTER  TWO:  Nest  Introduction  Success  and Breeding  1 Chronology  4  Introduction  4  Methods  6  Results  11  Nest  Success  11 -  Nest  Predation  11  Nest  Site  12  Predator Nest  Behavior  20  Flooding  Seasonal Nest  and N e s t i n g Cover  22  Water  Level  Fluctuations  25  Desertion  27  Discussion  28  Nest  Success  Nest  Predation  Nest  Flooding  Nest  Desertion  Cover,  and Renesting  Predator Behavior  28 31 . 32 33  and Water  Level  Fluctuations 34  Conclusions  35  V  CHAPTER  THREE:  Feeding  Behavior  and  Survival  of D u c k l i n g s  .  37  Introduction  37  Methods  39  Results  45  Duckling Female Time  Survival  Behavior  Budget  Diving  45 45  of Ducklings  Duration  and  49  Feeding  Intensity  of Ducklings  ..  Discussion Time  54  Budget  Diving  of D u c k l i n g s  Duration  and  57  Feeding  Intensity  of D u c k l i n g s  ..  Conclusions CHAPTER  52  58 59  FOUR: F o o d  f o r Ruddy  Ducklings  61  Introduction  61  Methods  62  Results  64  Food  o f Ruddy  Seasonal  Ducklings  Abundance  64  of Chironomidae  Food  Density  and C h o i c e  Food  d e n s i t y and C h o i c e  of Patches  and  Zygoptera  ....  w i t h i n Ponds  70  of Ponds  70  Discussion Food  72  o f Ruddy  Seasonal  Ducklings  Abundance  72  of Chironomidae  Food  Density  and C h o i c e  of Patches  Food  Density  and  of Ponds  Choice  Conclusions CHAPTER  FIVE:  68  and  Zygoptera  w i t h i n Ponds  ....  73 74 75 76  General  Discussion  77  References  Cited  80  APPENDIX ONE: D e s c r i p t i o n APPENDIX  TWO:  Ambient  Comparison  of  of Study  Temperature Ambient  Site  86  and Late  Breeding  Temperature  in  Spring  88 and  Summer Ruddy  89  Duck  and American  Coot  Nest  Temperatures  Conclusions APPENDIX  THREE:  92 Predation  of Flagged and Concealed Nests  Conclusions APPENDIX  i n Ruddy N e s t s  98 98  Chronology  Seasonal Nest  vegetation  Composition  Laying  Patterns  Parasitism  Conclusions  .. 95 96  FOUR: G r e e n  Nest  91  99 i n Vegetation  Growth  101 .  103 103  vii  LIST  OF  TABLE  1: V e g e t a t i o n a n d N e s t  TABLE  2: V e g e t a t i o n M e a s u r e m e n t s  TABLE  3: C o m p a r i s o n  TABLES  Site  of American  Measurement i n Spring  Coot  and  Descriptions  a n d Summer Ruddy  Duck  14 Nest  Sites TABLE  16  4:  Concealment  a t American  Coot  a n d Ruddy  Duck  Nest  Sites TABLE  19  5: C o m p a r i s o n  of Successful  a n d D e s t r o y e d Ruddy  Nest  Sites TABLE  21  6:  Coot  Comparison  Nest  of Successful  and Destroyed  American  Sites  21  TABLE  7: A v i a n  Predators i n Spring  TABLE  8: R a v e n  Behavior  TABLE  9: W a t e r  Level  TABLE  10: N e s t  Success  i n Spring  Fluctuations o f Ruddy  a n d Summer  23  a n d Summer i n Spring Ducks  24 a n d Summer  Reported  in  . . . . 26 Other-  Studies TABLE  7  30  11: N e s t  Success  of American  Coots  Reported  i n Other  Studies  30  TABLE  12: Mean  Duckling  TABLE  13: A l e r t  TABLE  14: F r e q u e n c y  Behavior that  Age f o r Age C l a s s e s of Females Broods  with  were  1A t o 2C  Broods  Observed  48 in  Cover TABLE  15: R e s t i n g  TABLE  16: D i v i n g  TABLE  17: F e e d i n g  41  Bulrush 50  and Feeding  Behavior  of Ducklings  Durations of Ducklings Intensities  of D u c k l i n g s  51 53 53  viii  TABLE  18: R e p r o d u c t i v e  TABLE  19: F o o d  TABLE  20:  Ducklings TABLE  Habits  Success o f Ruddy  Invertebrates Collected  21: D e n s i t y  of  and  a t Ponds  of Ducks and Coots  56  Ducklings  65  Seeds  i n Esophagi  26  54  and  I n v e r t e b r a t e s a t Ponds  of  Ruddy 67  26  and  54  67  ix  LIST  OF F I G U R E S  FIGURE  1: P r e d a t i o n a n d P a r a s i t i s m  o f Dummy  Nests  FIGURE  2: V e g e t a t i o n  Density  in  Height  and  13  Spring  and  Summer FIGURE  18  3:  Ducks  Survival  from  E g g t o 2B A g e C l a s s  f o r Young o f  and Coots  .  FIGURE  4: D u c k l i n g S u r v i v a l  FIGURE  5:  Densities  Naiads  in  Areas  of where  from  Hatching  Chironomid Females  t o 2B A g e C l a s s  Larva  Ruddy  46  and  . 47  Zygoptera  Ducks F e d Most and  Least FIGURE  69  6:  Naiads FIGURE  of  8:  Spring  Average  Larva  and  Zygoptera  Ducks d i d not Breed  71  Area  Minimum  87  and  Maximum  Temperatures  in  a n d Summer  90  9: P r e d a t i o n o f  Dummy  Chironomid  on a Pond where Ruddy  7: M a p o f t h e S t u d y  FIGURE  FIGURE  Densities  Unflagged,  Flagged  and  Concealed  Nests  97  FIGURE  10: C h r o n o l o g y  of Clutch  Initiation  FIGURE  11: P a t t e r n s o f V e g e t a t i o n G r o w t h  i n Ruddy  D u c k s .100  i n 1983 a n d 1984 .102  X  ACKNOWLEDGEMENTS  I Smith and  wish  (committee J.P.  me  other  Eadie,  Mark  Ertis,  My  Dublin,  Bob  Emery,  with  Shawn  forest  of  Financial  the  Service  and  Brown  forthis  project  Support  Thompson  Fund  Somerville,  have  a s do  Susan  came  Andre  be  Breault,  in  the  from  the  lab  inpenetrable and  other  Somerville.  the  Canadian  support  Finally,  I  given  me  s o I am d e d i c a t i n g  and  assistance  words  and personal  support  have  suggestions  of C h r i s t i n e  Fellowship.  and moral  not  who  i n the  misspelled  David  Unlimited),  for  be l o s t  advice  may  John  Powell,  and  Useful  still  i f i t weren't would  Rob  Blachford  (Ducks  have  and Jane  Merkt,  thanks,  Garreau,  I'd  modifiers,  the financial  Richard  I  they  my  John  Unlimited). samples  though  anxieties.  Rory  Juan  DeLannoy,  Alistair  from  John  Bernard,  deserve  computer  (CWS),  Research  Robert  often,  and  came  Leudke,  who  difficulties  Gauthier,  Dave  member),  biologist) permit  Florence  the e d i t i n g  assistance  acknowledge  him.  misplaced without  James  father,  (Ducks  Somerville  nightmares  Wildlife  Boyd  invertebrate  Bryce  Bowerman,  work  Service  Wilf  Mesa,  certainly  field  (committee  t o p i c 'changes,  Fryxell,  Graystone  ( s u p e r v i s o r ) , J.N.M.  Neill  Wildlife  Kate  d i f f u s e d my  Boychuck  counting of  They  Shirley  help  W.E.  encouragement  i t .  successfully  Ron  Joy  Sinclair  friends Gilles  John  Chiasson,  provided  and  (Canadian  disasters.  Alyre  realized  Dr.  thesis  Cheesman,  McAlary  A.R.E.  through  Holly  Werring,  Dr.  member),  Savard  supported and  t o thank  to this  from  wish t o by  my  thesis to  1  CHAPTER  ONE  General, I n t r o d u c t i o n  Birds for  a  breed  particular  climates,  most  moreover, timing  of  Perrins, the  of  this  study  i s to  of  high  Discussions success birds  than  almost  breed  1968).  when  Often a  consider,  though  examine  of  the  always food  some  influence  a  i s most as  f o r young  reproductive  1954;  may  reduce  Despite  these  success  hatched  more  1980).  young) 1974;  later  The  than  aim  of  affect  the  jamaicensis)  and  that  may  achieved. reproductive  Lack's  hypothesis  that  abundant  (Lack,  1954,  i f i t were i s an  only  young  less  determine  David  for  McKnight, or  the  example,  nest  more  (Oxyura is  that  allow  high  month  that  to  the  season  winter.  or  1954);  (Lack,  p o s s i b l e and  factors  Ducks  i s presented  not  late  i n the  one  success  refer  i t is clearly  rates  1941;  the  factors  food  survival  (Bellrose,  of  temperate  (Lack,  For  exhibit  nest  Ruddy  While  seasonally,  are  (Low,  f o r young  idea  later  produce  America  In  success.  hatch  Ducks  they  1968).  summer  fledge before  reproductive  this  theory.  in  that  that  survival  breeding  how  and  Ruddy  in North  higher  Breeding  clutches that  1977),  waterfowl  consider  grow  duckling  most  timing  to  of  Siegfried,  young  characteristic  studies suggests  reproductive show  are  (Lack,  various  nesting attempts  drawbacks,  high  for  that  s p r i n g and  from  1966).  f o r young  (proportion  area  in  species  than  1965,  potential  and  breed  affects  within early  number  time  birds  breeding  hatch  seasons  geographic  information  comparisons that  in restricted  fact  important  factor  success  a  that and  rather  factor can  thus,  to  vary affect  2  timing  of  breeding.  (Braestrup, and  1940),  t i m i n g of  breeding. factors than  that  The  question  Ducks  has  Biologists 1980), have that  and  food  observed  vegetation breeding Siegfried  exhibited I season  also  also  that  1966;  breeding  predation  Perrins,  influence  approach  to  1966)  timing  young  their  consider  they  energy  to  most  fat  the  and  more  suggested  (Gray,  Ruddy  Ducks  in  the  Ruddy  that in  at  season (1976a)  incorporated  the  green  Ducks  vegetation for  breed  suggested  Siegfried  that  delay  nesting.  females  the  have  spring,  breeding  with  those  b i o l o g y of  why  i n the  grounds  Ruddy  Ducks  breed  late  in  spring  to  those  existing  by  breeding  breed, in areas  existing  early  but  stores.  understand  Ducks  in  system  (1980)  late  hypothesis  arriving  breeding  comparing:  Ruddy  the  literature.  of  Gray  always  to  the  1976a)  green  of  mating  abundant  almost  the  females  in  hypothesis.  reserves  substantial  on  require  discussed  timing  question.  Lack's  nests  the  (Siegfried,  was  females  i t because  when  of  studying  must  attention  this  conditions existing  Ducks 3)  biology  Ruddy  because  can  research  discussed  into  (Lack,  determines  little  conditions existing  later 2)  received  attempted by  what  supported  insufficient rejected  of  f o r Ruddy  that  1969)  shown  young.  breeding  thus  females  t i m i n g of  conducting  briefly  and  1)  for  has  comprehensive  determine  food  for  (Harris, a  just  Ruddy  food  moult  Thus,  Research  used  in areas  breeding  that  species  they  do  including  Ruddy not  use,  Barrow's  the  3  Goldeneye albeola) that I  of  (Bucephala and  feeding  various  of for  abundance  of  temperature to  British  first  food  The  for  of  the  study  the  of  (Bucephala  americana)  was  Canada area  nest  clutch  to  rapid  green  influence  of  conducted area  i s given  I  in  in Chapter Chapter  species.  and  i n an  in  and  ducklings Two  loss  ducklings  breeding  i n Appendix  Columbia,  description  Ruddy  late  examine  breeding.  (Fulica  causes  of  the  essential  Coot  Bufflehead  Ducks.  behavior  survival  Four  American  Ruddy  consider  clangula),  growth also  Chapter  i n the called  Chilcotin Becher's One.  of  since  young  Three,  factors  i n Appendix  Two,  and  discuss  vegetation these  One  in on  is the'  ambient Appendix  timing  of  parklands  of  Prairie.  A  4  CHAPTER Nest  Success  and  Breeding  TWO  Chronology  i n Ruddy  Ducks  and  Coots  Introduction  American when  nesting  fluctuate.  cover As  predators the  Coots  or  first  nest in  Collins,  1954;  result,  is the  than  vegetation.  Nesting  and  Although Ruddy  relative  other  Ruddy  Ducks The  nest  to  chapter  success  American breeding such  as  1955).  of  Ruddy  Coots? late?  2) It  cover  species  that  Several summer  than  may  that on  the  are  it  suggest  seasonal  of  they  First,  in  breed  emergent  be  taller  possibility  of  success  success  nest  1)  How  compare for  of  to  Ruddy  does  the  that  of  Ducks  of  differences in  desertion breeding  considers  that  and  Ducks  Nest  advantages  timing  success  nesting  questions:  Chilcotin  and  if  Coots.  two  the  how  the  spring.  of  i n the  i n f l u e n c e when  factors in  as  the  1980).  time  (Miller  sites  high  to  nest  likely  precludes  may  nests  second  Ruddy  would  fairly  ponds  high  time  vegetation  lose  Coot  this  flooding  addition,  and  (Bellrose,  What  species.  a  nest  contrast,  exhibit  Ducks  affect  can  similar  focus  differentially  to  typically  late  on  expected  in  breeding  high  levels  though  at  examines  predation,  In  In  Coots  will  be  they  is  i n emergent  water  ( i e . renest)  waterfowl as  and  However,  Ducks  i s not  spring  might  literature  Kiel,  renesting,  poor  they  lost  American  denser.  i n the  is often  flooding.  reported  later  a  nest  of  factors  nests in  might  these  characteristics  of  two each  breed. predation  cover  may  i s lower  increase  in  the  later  in  5  the be  season  and  d e s t r o y e d by  behavior when  may  thus  fewer  predators differ  Duck  (Schrank,  between  spring  Ducks  nest.  P r e d a t o r s may  less  often  i n the  summer  may  be  lower  i n the  lead  to  fewer  rewards,  sources  of  territorial nest  Ruddy  food  females  vulnerable  and  (Jones  (Ryder,  site,  summer,  than  when  1959),  both  Ruddy  Ducks  incubate  the  eggs,-  predation  and  nests  Second,  to  spring.  and  search Nest  concentrate  sexes are  Ruddy  therefore  for  density would  on  other  S i n c e Coot  incubate  not  summer  for nests  1972).  may  predator  nest  searching  Hungerford,  and  Coot  ponds  i n the  p r e d a t o r s may and  than  Coots  visit  therefore  whereas  to  nests 1972).  Ruddy  nests  the  Ruddy  and  are  defend  territorial  and  only  Ducks  may  be  more  from  breeding  excluded  earlier. Flooding when nest  may  rainfall above  other  ducks  may  the  that  by  ambient  nests  the  cost  have  In  breeding  Ruddy  females  may  reduce  found  that  early  breeding  stored  energy  nest  females ducks.  than  temperatures  more  Coots as  may  or also  a  cold  incubation feed  more  Thus,  high  energy  often  or  higher  spring  and  Coots  flooding  than  common to  Coots  affected desert complete  are  Further,  females  summer  may  reserves to  during  warmer,  Tome  (1984)  incubation  than  may  less  incubation than  in  be  temperatures  costs.  complete  to  less  spring,  Ruddy  Ducks  in likely  when  in  cavities.  be  incubation  later  to  in  than  Ruddy  vulnerable  insufficient  By  i n summer  Because  ground  of  incubation.  Ruddy  are  desertion  The  they  common  greater.  on  temperature.  because  less  they  nest  nest  in spring.  be  be  water,  Finally, than  also  those  require and of  maintain Coots  (see  6  Appendix In  Two). this  chapter,  Coots  and  assess  the d i f f e r e n c e in cover  Ruddy  compare  I describe  Ducks.  predators determine Finally, predation  these  Water  early the  and  risk  dummy  level  nest  early  available  vegetation  available  to  Coots  and  behavior  of  i s compared  i n order  to  compare  i n the season  and  and  predation  that  Ducks  to American  i n the season  f l o o d i n g and  late  o f Ruddy  changes are described,  experiments  and  sites  t o the marsh  late  of  nest  are  at  these  times.  experimentally  nest  discussed.  Methods  Nest  Success In  shoreline August  1983, of  searched all.  were  known.  a map.  felt  pen  Coots  time  1.  When  with  a by  Nest  of d i s c o v e r y  of  of  and two  searched  were  A l l eggs  characterized Table  were  1  were  number  was  sites and  ponds  and  several  each  Most of  1  egg  nest.  Each  at  least  determine  and  searched were  seven  times  a l l  was  and  ponds  i t s location  pairs  was  nests noted  labeled nest  of  in  site  was  described  in  once between  the  measurements  revisited to  July was  total  band  the l o c a t i o n s of t h e i r  in that  hatching  5.  for a  discovered,  unique  were  twenty  f r e q u e n t l y when  and  counted  measuring  between  August  less  vegetation  once  weeks,  incubating  a nest  emergent  ponds  each  May  intervals  Ponds  and  1984,  between  at  the  of seventeen  In  ducks  on  searched  each  9.  periodically  in  I  i f  nests  were  7  T A B L E J_ Vegetation  and  Nest  Site  DEPTH AT DEGREES  #  OF  NEST  NEST OPEN  ENTRANCES  N E S T CONCEALMENT  WIDTH OF  MAXIMUM  VEGETATION  VEGETATION  HEIGHT  GREEN V E G E T A T I O N  HEIGHT  DEAD V E G E T A T I O N  HEIGHT  GREEN  VEGETATION  DENSITY  DEAD V E G E T A T I O N  DENSITY  TOTAL DENSITY  Measurement  Descriptions  - water depth at nest - # of d e g r e e s (0-360) i n t h e v e r t i c a l plane of the nest c i r c l e which were f r e e o f c o v e r (an e s t i m a t e of c o n c e a l m e n t o f e g g s when t h e n e s t was viewed from the s i d e ) - # o f ramps o f v e g e t a t i o n a l l o w i n g e n t r a n c e t o and e x i t from nest - v i s i b i l i t y of n e s t s from above (2 c a t e g o r i e s : o p e n a n d concealed). - s h o r t e s t d i s t a n c e , f r o m shore to the edge o f t h e marsh (where open water began) - h e i g h t ( w a t e r l i n e t o apex of stem) of t a l l e s t s c i r p u s stem - h e i g h t o f 1.0 g r e e n s c i r p u s s t e m s w i t h i n a meter of the nest - as above, except h e i g h t of p r e v i o u s y e a r s ' d e a d stems were measured - # of green s c i r p u s stems i n a 0.30 X 0.30 m q u a d r a t placed within 1 m of nest (or at midpoint of width if extensive vegetation measurement) - as above except the # of dead s c i r p u s s t e m s was recorded - t h e sum o f g r e e n a n d d e a d v e g . densities  8  destroyed a  by p r e d a t o r s ,  nest  were  and a l s o  counted.  Nests  hatching  date  and  examined  checked  for  new  broods  nest  loss  using  to predation  chi-squared  Nest ing  compare available  monitored again  for  of Coot  in mid-July  measured  time  and  Ruddy  laid  in  at the predicted  eggs.  also.  nest  sites  available  when  Ruddy  Ducks  two p e r i o d s : of  1984.  vegetation at thirty  Nests Duck  sites  numbered  orange  stations,  late  (These  on e a c h  indicated I measured  Ponds  were  success,  and  were  compared  vegetation  vegetation  stations,  only  width  was m e a s u r e d .  establish  whether  statistical  measurements  were  vegetation  compared  by  nine  lakes  were  June  shore.  density. (More  t-tests.  the was site  spray-painted At odd-  dead  vegetation  green  vegetation  At samples  Mean  of each  stations.  differences existed width.)  as  vegetation  Rocks  thirty  1984, a n d  to  the l o c a t i o n  width,  dead  with  Emergent  height,  and  nested  be r e f e r r e d  height,  density,  Coots  to early  maximum  green  emergent  will  the  height,  summer  May  pond,  on t h e  when  nested,  measurements.)  i n d i c a t e d by m a r k e r s  fluorescent  and  revisited  unhatched  at this  a l l eggs  tests.  during  extensive  being  were  that  Cover  To those  t o ensure  values  even-numbered were  needed  between  to  spring  f o r nest  site  9  Nest  Predation  I nest  compared  a n d summer  referred  bulrush  predation when  t o as  27,1984,  at  Ducks  placed  nest.  were  nest  sites  arranged  located  at a density  within  t h e emergent  dummy  nest,  marked  by s e c u r i n g  distance  and  of  larger  had  f l a g g i n g tape  five  or  two  more  on  two.  or  meters  ponds Nest  near  from  May  range (These  These  pond,  be  scirpus  the  nests.)  small  on  i n 1983.  per  Coots  will  dead  within  dummy  vegetation; ponds  from  discovered  of one or  when  Beginning  values  r e f e r r e d t o as flagged-unconcealed  were  A.)  constructed  measurement  Duck  in spring  (This experiment  experiment  nests  with  Ruddy  of nests  nest  dummy  sites  at  Ruddy  dummy  thirty  measured are  Experiments  and  nests were  h a d o n l y one  l o c a t i o n s were  the  the nest  shore  at  a  (see Appendix  Three). Five were  chicken  white  Dummy  the  nests  (1980), period each Nests were  test.  were  were chosen  placed  Duck  visited  a t weekly were  days  Duck.)  Beginning  i n each  eggs  two  nest.  b u t were  days  intervals.  twenty-four  o f a Ruddy  visit.  were  Ruddy  twenty-four  predators Nest  like  nests  subsequently  eggs  days  slightly  after  The f i n a l old.  (Chicken  visit  (According  Egg l o s s  from  each  the  procedure  nest  as before,  to  that  was  had  predation  learned  bias  to associate  was c o m p a r e d  a nest  statistically  incubation  repeated.  b u t new  introduced location by  when  to Bellrose  was  and d i s t r i b u t e d no  and  was r e c o r d e d a t  constructed ensure  was made  of the average  14,  smaller.)  construction  i s the length  July  eggs  the  sites  because  with  eggs.  chi-squared  10  Identification  To  the  predators Common  Eagles  e)  away).  (15  upon  nests  compared  early  and  were  applied  number the  of  Nest  estimated ponds  and Ruddy  were  the  during  determine  close  on  ground,  and  and  late  predators  early  and  late.  c)  flying  i t  predators  and  day  periods  of  Chi-squared  differences i n the  low  carrying  avian  early  flying  or  of  predators  b)  and  and  experiment.  Bald  calling,  egg  twenty-four  (Buteo  d)  an  kinds  pond.  Behaviors  gliding),  flapping),  a  and  observed.  the  statistical  to  cyaneus),  nest avian  Hawks  consuming  the  predation  seen  were  higher-  numbers  potential  Red-tailed  flapping  (observed  of  (Cireus  walking  or  responsible for  the  tests  between  season  and  the also  Density  Nest  14  of  they  corax),  m.-  m.  season to  avian  behavior  15  observed  late  a)  be  behavior  Harriers  :  fast  behaviors  might  leucocephalus)  than  I  and  whenever  Northern  (lower  and  species  (Corvus  included  preying  the  noted  (Haliaeetus  slow  high  what  Ravens  recognized  Predators  location  were  jamaicensis),  and  Nest  determine  predation,  Only  of  density by  counting  twice:  once Ducks  per  once  during and  the  early  number  during  peak  Coots  pond  Ruddy nested  of  peak  Coot  Coot  Duck on  and  late and  nesting  nesting  a l l of  the  i n the  Ruddy (May  (July 14  Duck  was  nests  27-June  14-Aug  ponds  season  6).  studied.  on 19)  Both  11  Water  Level  Fluctuations  Fluctuations Coots  were  i n depth  measured  with  twenty-three  p o n d s o n May  recorded  28,  May  of ponds  June  15,  depth 10,  July  used  by  monitoring  1984.  Ruddy stakes  Changes  10 a n d A u g .  Ducks  and  installed  in  depth  on  were  4.  Results  Nest  Success  A and  chi-squared  unsuccessful  different Ducks was  was 70.0%  from 60.9%  test  showed  that  nests  o f Ruddy  those  of American  Ducks  (n=46), whereas  (n=146).  Nest  frequencies  Coots.  nest  success  were  was  not  Nest  success  of  calculated  of  successful  significantly  success  by  of nests  i n which  at least  one  egg h a t c h e d  total  number  of nests  i n which  at least  one  e g g was  the  by  the  nests  were  laid.  Predation  A  chi-squared  destroyed  by  nests=46,  total  Coot  Coots  dividing  number  were  Ruddy  American  total  Nest  of  predators  destroyed nests  test  were  Coot by  than  showed were  nests=146). predators,  destroyed.  that Coot  fewer  nests  Eleven whereas  Ruddy  (p<.005;  percent  total  o f Ruddy  twenty-eight  Ruddy nests  percent  of  1 2  Experiments with  the  suggested  season  experiment  (see also  A, p r e d a t i o n  compared  to  o f dummy  different  from  in  missing)  within  t h e summer  only  first by  i n summer  2 days.  female  rarely  Nest  parasitize  cover  than  compared  to  test  season  width  of emergent  season  might  destroyed  nests  n=30). ( a l l5 whereas  within the  were  parasitized  My dummy  nests  females,  s i n c e Ruddy  waterfowl  (Joyner,  i n t h e summer  of  Coot  nests.  early  idea.  likely  were Ducks  1973).  of measurements i n Table  significantly  2.  different  values  than  in  o f Ruddy  values  from  Table  nests  early  taken those  and l a t e  2).  early  taken Maximum  of were  and  F o r a l l measurements  values  i s in  i n t h e season  average  taken  i t  Characteristics  and l a t e  The  v e g e t a t i o n , mean  p  test;  destroyed  e x p l a i n why p r e d a t i o n  present  a r e shown  (t-test,  significantly  Cover  this  intervals  1984  were  of other  predation  vegetation  season  by p a r a s i t i c  may b e g r e a t e r  emergent  confidence  i n t h e summer.  nests  s p r i n g and thus, less  o f dummy  was  1 ) . The  of the experiment,  was c o m p l e t e l y  nest  early  (Figure  chi-squared  completely  varied  I n dummy  i n s p r i n g was  2 days  percent  nests  and Nesting  Nesting  was  Ducks  f o rRuddy  Site  the  Seventeen  Ruddy  mistaken  the first one n e s t  season  (p<.00l; were  predators  established  the  destroyed  to  Three).  nests  in  the s p r i n g a l l but 2 nests  eggs  loss  Appendix  late  nests  that  nest  o f dummy  predation  proportion  In  that  in  95% the  except i n the  late  in  the  height of  13  O o  n = 30  LATE o  CO  EARLY  o I-  z  UJ CJ QC UJ  0.  o  n r 30 n =30  o  (VI  n =30 o  J  NESTS DESTROYED BY PREDATORS  FIGURE  j_ :  predation, late  season  Comparison  egg  predation  NESTS PARASITIZED  of  the proportions  and nest  of  dummy  nest  p a r a s i t i s m i n the e a r l y and  14  TABLE 2 E x t e n s i v e V e g e t a t i o n M e a s u r e m e n t s : T h e s e measurements were taken a t a t i m e when m o s t A m e r i c a n C o o t s b e g a n t o l a y e g g s ( E A R L Y ) a n d c o m p a r e d t o t h o s e t a k e n a t t h e t i m e when m o s t R u d d y D u c k s b e g a n to l a y (LATE).  EARLY VEGETATION  MEASUREMENTS  ***Maximum V e g e t a t i o n Height ***Green V e g e t a t i o n Height ***Dead V e g e t a t i o n Height Width of V e g e t a t i o n ***Dead V e g e t a t i o n D e n s i t y ***Green V e g e t a t i o n Density ***Total Density ***significant  LATE  MEAN  95% C.I .  1 .2 0.21 0.79 6.3 21 17 37  0.05 0.018 0.051 0.33 1. 5 1. 1 1 .7  difference  p<.00!  MEAN  1 .7 1.21 0.46 6.3 6 26 31  95% C.I . 0.04 0.121 0.043 0.29 0.9 1. 1 1 .2  1 5  vegetation, density Ruddy  height  were  different Since,  that nest  cover  reducing Not  density  rates  have  later  and dead  Coots  and  when  Ruddy  with  the  resulted Ruddy  from  in  Ducks.  Ducks n e s t e d  nests  support  vegetation  nested  the  Dead  height  suggested  to understand  of  nest  than  predators  that  rather  hypothesis  vegetation  were  greater  cover  than  3 shows  mean  values  taken  a t Ruddy  Duck  and Coot  sites  o f t h e two s p e c i e s  showed  that  the nest  measurements  were q u i t e  sites  taken.  nest  differed  The  dead  density  were  sites  than  a t Coot  nest, s i t e s .  green  vegetation  Ruddy  height  (t-test,  was  later  that  density,  earlier  in  taller when  also  and  Ruddy  (Table  were  2),  on  similar,  careful  significantly  less  significantly  at  height, Ruddy  greater  vegetation shorter,  predation.  the  nest  measurement  i n 8 o f t h e 10  vegetation  3 for p values).  in  of measurements  Although  The green  exhibited  nest  limits  vegetation  the extensive  be c o n s i d e r e d  sites.  significantly  see Table  Ducks, l i k e  the season  must  and c o n f i d e n c e  vegetation  sites  sites  the influence of cover  Table  in  cover  when  nested.  order  of  consistent in  i n the season.  Coots  Characteristics  nest  i n the season  camouflaged  taken  result  when  for  vegetation  predation.  This  earlier  green  later were  and denser  may of  greater  season.  Ducks  taller,  and  differences  a l l measurements  total  denser  results  predation  the risk  was  the  These  cover  cover  vegetation greater  seasonal  was  spring,  green  significantly  Ducks n e s t e d .  hypothesis  in  of  and  dead  Duck  nest  d e n s i t y and  a t Ruddy  Thus,  nest  Duck sites  measurements  late  less  dead  dense  16  TABLE 3 Comparison  NEST  SITE  o f Ruddy Duck a n d A m e r i c a n  MEASUREMENTS  ***Number o f N e s t Entrances • D e g r e e s Open ***Depth a t Nest ***Maximum V e g e t a t i o n Height ***Green V e g e t a t i o n Height *Dead V e g e t a t i o n Height Width of Vegetation **Dead V e g e t a t i o n Density ***Green V e g e t a t i o n Density Total Density significant significant significant  Coot  Nest  AMERICAN  COOT  MEAN  95 % C.I .  MEAN  1.12 60.0 0.43 0.87 0.46 0.82 11.85 22.4 16.6 39.0  0.069 7.84 0.018 0.066 0.069 0.052 1 .543 1 .80 2.16 2.10  0.68 40.2 0.33 1 .68 1 .30 0.61 1 1 .84 14.8 -25.1 39.9  difference difference difference  p<.05 p<.0l p<.00!  Site  Measurements  RUDDY  DUCK 95 % C. I . 0. 216 1 3.71 0. 0 4 9 0. 106 0. 092 0. 123 2. 465 3 .92 3 .52 3 .90  17  vegetation  and  taller,  Significant emergent Coots  vegetation  Ducks  available 2).  average  than  are  The  nest  sites.  Table  1  sites  nest  to  greater  where  estimate  the  squared nests  may  those  from  test; be  than  the  Coot  nest sites  d i f f e r e n c e s between  Coot  and  nest  a  and  to  would  were  be  visible. Nest  of  to  a  nest  most  concealed  vulnerable  approach  visible  to  Table  3  visibility  of  to  Ruddy  Duck  may  For  have an  avian  nests  of is  nest an Open  predators. significantly  (table  that  predators.  been angle  predators.  was  suggests  Ruddy  side.  concealment  nests  avian  see  Comparison  Coot  evidence  at  from  avian  open  less  any  there  the  Ruddy  degrees  the  from  open,  result.  concealed  This  marsh  degrees  and  (t-tests;  estimated  the  predator eggs  judged  of  sites  approaching  visibility  of  less  and  Figure  within  similar  p<.05).  see  nest  measurement  entrances  that  average  the  Coot  These  a  frequency  different  at  gives  The  of  significantly  than  while  vegetation  were  and  were  average  for definition)  nest  nests  the  Duck  entrances,  that  of  Ruddy  the  cover  nest  chance  concealment  greater  of  more  the  with  position  number  predators  with  and  other  The  values).  nests a  suggested  vegetation,  season.  construction  vegetation  the  the  values.  p<.005;  alike  in  site  (t-test,  nested.  late  sites  green  average  than  they  and  p  density  nest  the  greater  when  early  for  with  available more  nest  taller  selected  thus  Duck  sites  between  average  species  are  (see  the  with  vegetation  vegetation.  existed  and  sites  s e l e c t e d nest  sites  Duck  values  nest  dead  Both  green  differences  selected  Ruddy  denser  4;  Ruddy  chiDuck  18  Coot Nest a i t o  Spring Veg. 8 l t o  Ruddy Noat S i t e  Sumac Vflfl. 81ta  FIGURE Duck at  2 and  : a) Comparison American  extensive  of green  Coot  vegetation  nest  vegetation  sites  measurement  with  height  green  sites  in  at  vegetation the  Ruddy height  spring  and  summer b) C o m p a r i s o n Duck at  and American extensive  summer  Coot  nest  vegetation  of  dead  sites  vegetation  with  measurement  dead sites  density  a t Ruddy  vegetation  density  i n the s p r i n g and  19  TABLE  4  Comparison  o f Ruddy  Duck  and American  RUDDY DUCK N E S T S  Concealed  Open  Coot  Nest  Concealment  AMERICAN  COOT  26  46  4  21  NESTS  20  Finally, probability expect  if  of  a  cover nest  being  differences  destroyed denser  nests.  cover  and  degrees  nest  sites  and  6  at  Such  open,  show  at  nest  sites  values  and  nests  Ruddy  nests  may  measurement successful heights  ones,  and  similar dead dead cover  were  lower  only  the  by  at  being ,  not  and  destroyed  successful Tables  Ruddy  than  for  different. to  be  nests.  different, nest  Most  vegetation  appeared  Coot  Destroyed  nests  Duck  5  Duck  cover.  between  Ruddy  and  entrances  predators.  nests  and  measurements  significantly  Coot  shorter,  at  of  poorer  significantly at  nest  destroyed  were  destroyed  found  nests  by  would  taller  predators.  in  for  nests  was  fewer  differences  destroyed  height  taller  more Only  the  taller  sites.  Thus,  at  Coot  nests  that  were  different  early  i n the  season  when  predators.  Behavior  Predator Coots  located  s u c c e s s f u l and  vegetation  Predator  been  and  vegetation  destroyed  have  w a t e r "depths  than  was  destroyed  the  successful  limits  Coot  were  but  Successful  and  one  include  by  confidence  Duck  increase  concealment  that  values  of  might  nest  did  predator,  sites  destroyed  and  s u c c e s s f u l Ruddy  a  vegetation),  greater  describing Coot  nest  green  site  by  differences  and  mean  nest  destroyed  between  (especially  than  the  nest  behavior as  be  compared  Predators  may  visit  later  the  season  in  may  to  ponds  to  and  thus  later  search rarely  when  for  Ruddy  nests  destroy  Ducks  less  Ruddy  nest.  frequently  nests.  Table  21  TABLE 5 Comparison  of S u c c e s s f u l and Destroyed  Ruddy  Duck  DESTROYED NESTS VEGETATION  MEAN  MEASUREMENTS  # of nest entrances D e g r e e s Open *Depth a t Nest Maximum V e g e t a t i o n Height *Green V e g e t a t i o n Height ***Dead V e g e t a t i o n Height Width of V e g e t a t i o n Dead V e g e t a t i o n D e n s i t y Green V e g e t a t i o n D e n s i t y * ***  TABLE 6 Comparison Sites  significant significant  0.3 29 0 .10 1 .10 0 .93 0 .30 6.7 0 1 5  difference difference  # of Nest Entrances D e g r e e s Open Depth a t Nest Maximum V e g e t a t i o n Height Green V e g e t a t i o n Height *Dead V e g e t a t i o n Height Width Dead V e g e t a t i o n D e n s i t y Green V e g e t a t i o n Density *  significant  MEAN  1.1 56 0.41 0.79 0.45 0.90 9.7 23 18 difference  SUCCESSFUL  NESTS  MEAN  95% C.I .  0.65 11.5 0.095 0.020 0. 1 29 0.024 9.34  0.7 67 0.32 1.71 1.41 0.65 12.0 1 5 28  0.26 69.0 0.055 0. 1 32 0.115 0.121 3.81 4.3 4. 1  10.1 p<.05 p<.00l  of S u c c e s s f u l and Unsuccessful  MEASUREMENTS  Sites  95% C.I .  American  DESTROYED NESTS VEGETATION  Nest  95% C.I . 0.17 10.8 0 .036 0 . 1 50 0 . 1 54 0 .089 2.18 3.3 5.4 p<.05  Coot  Nest  SUCCESSFUL MEAN  1. 1 66 0.43 0.88 0.45 0.78 1 2 21 1 7  NESTS 95% C.I .  0.08 21.8 0.024 0.083 0.081 0.071 1 .78 2.2 2.6  22  7  shows  that  spring were on  than  also  3  significantly in  t h e summer  observed  separate  preying  increased  difference  was  observed  observed  season  Table  upon 8,  and  season. late  i n the season.  have  been  and  feeding  average  vegetation  Nest  of  although  upon  adult  Ravens  vegetation  Red-tailed  summer;  Hawks  however,  this  Red-tailed  birds,  the  they  Hawks  were n o t  of Ravens  less  'flying  early low  frequently late were  'walking  only  seen  on g r a s s h o p p e r s  slowly'  observed  'walking  that  and  i n the was  i n the season.  on t h e g r o u n d '  The Ravens  and l a t e  were  was  early  only  This i n the  observed  on t h e g r o u n d '  abundant  during  may July  August. The  1.9  and  predation  The b e h a v i o r  to  in  p<.005).  i n t h e emergent  spring  t o prey  observed  test;  numbers  The b e h a v i o r  nest  were  nests.  significantly  behavior  The  the behavior  i s compared.  observed  nests  not s i g n i f i c a n t ,  to prey  In  upon  from  attempting  Ravens  (chi-squared  occasions.  observed  were  fewer  nests  was  density  5.9  p e r pond  of Coot  nests when  p e r pond Ruddy  and waterfowl when  Ducks  nests  American  i n emergent  Coots  nested  and  nested.  Flooding  Twelve flooded Flooding storms  percent  of  Ruddy  Duck  i n 1 9 8 4 , b u t no f l o o d e d C o o t o f Ruddy that  vegetation.  nests  swamped Almost  nests nests  was a p p a r e n t l y  and  overturned  a l l Coot  (n=46)  (n=146)  were were  found found.  caused  by two m a j o r  nests  in  c l u t c h e s had a l r e a d y  the  wind  emergent  hatched  when  TABLE 7 C o m p a r i s o n o f A v i a n P r e d a t o r s : T h e s e o b s e r v a t i o n s w e r e made a t a t i m e when m o s t A m e r i c a n C o o t s b e g a n t o l a y e g g s ( E A R L Y ) a n d c o m p a r e d t o t h o s e t a k e n a t t h e t i m e when m o s t R u d d y D u c k s b e g a n to l a y (LATE).  SPECIES **Raven R e d - t a i l e d Hawk Northern Harrier Bald Eagle Total **  significant  EARLY  LATE  20 3  6 8 3 0 16  24 difference  p<.0l  TABLE 8 R a v e n B e h a v i o r : T h e s e o b s e r v a t i o n s w e r e made a t a t i m e when most A m e r i c a n C o o t s began t o l a y e g g s (EARLY) and c o m p a r e d t o t h o s e t a k e n a t t h e t i m e when m o s t R u d d y D u c k s b e g a n t o l a y (LATE).  BEHAVIOR  PEAK  P r e y i n g Upon N e s t s * F l y i n g Low a n d S l o w l y F l y i n g High and F a s t W a l k i n g on t h e G r o u n d Calling *  significant  difference  COOT  NESTING  3 13 3 0 1 p<.005  P E A K RUDDY 0 0 1 2 3  NESTING  25  these  storms  occurred  incubated.  Wind  but  some  storms  and  observed  in  1983  for  either  flooding  due  to  heavy  rain  Coot  the  resulting  Ruddy was  nests  Ducks  not  or  were nest  still  l o s s e s were  American  observed  in  being not  Coots.  either  Nest  1983  or  1 984.  Seasonal  Water  Water Table  9.  Level  level Most  While  the  often  late  flooding  Fluctuations  fluctuations  ponds  became  prediction i n the  in both  shallower  that  season spring  in  as  yet  be  summer  1984  the  f l o o d i n g of  may and  i n ponds  true  are  season  ponds of  described  in  progressed.  would  occur  less  some  breeding  areas,  is apparently  uncommon  in  the  Chilcotin. Breeding level  later  to  in  no  by  season  Coot  nest  no  that  the  vulnerable  to  Ducks  been  has  Table  (Table  He  avian  predators  reported  speculated were  levels 5  to  be  at  6).  that  water  by  rare;  that  water of  levels dry  (1974)  Ruddy  nests  were  however,  the  have  water  may  Duck  nests  nesting nest  nests There  successful  however;  only  be  there  is  to by  be  more Ruddy  success  successful only predators  been lower  depths. at  and  water  were  depth  caused land  to  may  ponds  predators,  McKnight  most  water  shallower  Depth  Indeed,  respect  in  suggests  d e s t r u c t i o n by reduced  with  i n deep  d i f f e r e n c e between  predation.  80%.  sites  Water  tended  nests  with  disadvantage  nest  and  predators  correlated proof  a  Ducks.  significant  destroyed  be  Fewer  Ruddy  the  destroyed  or  may  dynamics.  available  was  late  was  because  responsible  26  TABLE 9 Comparison  of Water  Level  Changes  MAY  **Average D e c l i n e L e v e l (m)  i n Water  Average Increase L e v e l (m)  i n Water  Early  and Late  12 - J U N E  15  i n the Season  JULY MEAN  1-AUG.  MEAN  95% C.I .  95% C.I .  0.023  0.0032  0.096  0.0357  0.021  0.0079  0.019  0.0153  % of Observations where Water L e v e l I n c r e a s e d  30  NA  26  NA  *% o f O b s e r v a t i o n s where Water L e v e l Remained Unchanged  22  NA  0  NA  % of O b s e r v a t i o n s where Water L e v e l D e c l i n e d  48  NA  74  NA  * **  significant significant  4  difference difference  p<.05 p<.01  27  for  the  Ravens)  20%  nest  are not  loss rare  destroyed  nests  Ruddy  nests.  Nest  Duck  of  clutch  these was  in this  suggested  percent  Avian  study  area;  that  mammals  nests  When  development. begun.  of  Ruddy  Duck  were  found  during  completed.  incubated.  eggs  One  This-  nest  site  caused  the d a i l y  Nest  by  by  nests  might  have  never  found.  included  was  predators  however, not  nests  was  disturbance  been  Several  was  (especially  examination  birds  preyed  i n the nest  there 10  was  days  destroyed  when  the  desertion  known no  of upon  the  t o have  been  of  nests  female  were  died.  category.  embryo  incubation a  the  had  temperature have  been  thermometer.  although by  A l l but  after  sign  after  I checked  rapidly  Coot  just  d e s e r t i o n may  observed,  and  or  close . to  and  when  deserted.  not  not  Ruddy  abandoned  were  very  Two)  were  laying  deserted  site  Coots  nests  opened,  (see Appendix  desertion  subsequently  These  were  nest  monitoring  not  unknown.  Desert ion  Fifteen one  were  deserted  predators  and  incubated These  nests  so but  were  28  Discussion  Nest  Success  Nest  and  success  significantly Coots  nest  a  young.  approximately  hatched pairs  One  were  young. that  hundred  of  Coots.  their  first  Since  almost  although  nest  nest  is  proportion  ponds  a l l  loss  were  able  that  that were  there  Coot  were  nests  (ie.  successfully  Coots  on  this  nests  Coots  of  since  pairs  Coot  of  be  lost,  of  showed 70%  to  However,  nest  forty-six  the  not  Coots.  first  and  of  found  of  the  successful,  Thus,  lost  the  reflect  pairs  was  that  if  censuses  105  Ducks  from  time not  yet  nests)  Ruddy  different  does  discovered,  100  of  second  measurement hatched  Renest ing  was  average  high,  to  renest  successfully. In fewer was  contrast, nests  not  Ducks males.)  my  there.  i n the  second  she  nest)  peaks peak  attributed  i t to  nest  graphed  the  versus  the  noted  later  age  than  to  be  of  calendar  initiation. nests  of  the  same  the  renest,  and  b r e e d i n g ponds.  (It  female  accompanied the  was  Ruddy  Gray  several  that  phenomenon; bird  found that  egg two the  renested. however,  species,  experienced  in  longer  (one  concluded  females  Ruddy  Ducks  initiated  date, She  by  considerably  nests  f o r many more  to  since  that  season  number  since  on  pairs  suggested  breeding  nest  observed  counted  tended  (1980)  female  not  breeding  represented  (1974)  were  were  area  Gray  of  Misterek  females  to count  renested, the  When  distinct  Ducks  females  study  Although  California  laid  than  possible in  Ruddy  older  he  younger ones  29  (Klomp,1970; (1976a) in  found  Canada  no e v i d e n c e  and the United  While poor  Perrins,1970).  nests  nests  seasons  than  so  success  studies  (Table  be l o w e r  nests  that Nest  that  than  (pers.  populations  particularly  a n d s o Ruddy  Ducks  lost  Ducks  lose  a l l females  hatch  young.  High  species  has  that  (Table  of Coots  were  Ruddy  nest  success  comm.)  Goldeneye  Duck  Joyner  been  reported  success  o f Ruddy  11) a n d C o o t s  in  other  Ducks  tends  can  replace  are lost.  young  the  and  that  10); however,  o f Ruddy  Ducks  species  comm.) e s t i m a t e d  hatched  Ducks,  unlikely  almost  f o rt h i s  i n Ruddy  1983 a n d 1984  f o r Ruddy  that  (1976a),  States.  i t seems  o f two w a t e r f o w l  (pers.  in  usual,  rarely  nesting  to  of renesting  i t i s possible that  breeding  more  Siegfried  that  was n o t s i g n i f i c a n t l y  that  43%  breed  of  early.  Barrow's  in  the  Chilcotin  found  that  64% o f B u f f l e h e a d  Chilcotin  in  renested  renest  (Barrow's  hatch  fewer  1984.  in this  than  and  pairs  a n d Ruddy that  Savard  G.  pairs  Gauthier  hatched  species  those  P.  than  Goldeneye  Bufflehead  Thus,  Bufflehead  per pair  1984  Neither  area.  Goldeneye,  young  in  J.  less  young  nor Barrow's that  do  not  Duck)  appear t o  do r e n e s t  (American  Coot). Special this  c o n s i d e r a t i o n must  result.  renesting  These  b i r d s have  example,  newly  hatched  ducklings.  (Fredrickson,1970),  differences  higher  hatched  be g i v e n  Coot They  have  overall young are  less  to the implications  do  not  reproductive  are less unable  down  necessarily  than  success.  precocious  t o forage ducklings,  than  of mean For  newly  f o r themselves and a r e  less  30  T A B L E j_0 Comparison Studies  of Nest  Success  o f Ruddy Ducks  reported  % NESTS SUCCESSFUL  Bennett  SAMPLE SIZE  77.0  22  (1941)  73.2  71  M i l l e r and Collins (1954)  32.0  25  Rienecker and Anderson (1960)  54.7  64  Misterek  (1974)  53.3  30  Mcknight  (1974)  80.0  15  31 .3  1 50  Low  Joyner  T A B L E 11 Comparison Studies  (1938)  in Various  of Nest  (1977)  Success  of  American  Coot  % NEST SUCCESS  reported  in Various  SAMPLE SI ZE  M i l l e r and Collins (1954)  94.6  149  Kiel  97.0  380  Rienecker and Anderson (i960)  93.0  94  Gorenzel (1982)  78.9  330  (1955)  e ta l .  31  coordinated, more  vulnerable  ducklings. by  and  Boyd  This  experiment,  destroyed  found  crow  compared the  species  studied  for  i n spring  differences nests  may b e  than  are  Coot  was  found  young  (1961).  Clearly,  (see Chapter  i t  i s  2) i n o r d e r  were  higher  nests  cavities.  who c o m p a r e d  in  intensity  emergent  nest  predation.  i n the Cariboo  were  destroyed  Bufflehead, Cavity  nesting  none  nest  in the spring of  the  A similar  nests  result  waterfowl  of nest  nests  nest  was loss  southwestern Gilles area  Ruddy  birds  predation Nagel  Also,  British  Gauthier  tend  (1969)  Nest  not  a l l  Columbia  (pers.  o f B. C. a n d  Ducks  may  e a r l y and l a t e i n  difference.  by p r e d a t o r s .  unlike  b y t h e dummy  vegetation.  and c a v i t y  in  lower  summer.  no s i g n i f i c a n t early  almost  Coots  experience  established  destroyed.  versus  of American  breeders  supported  whereas  of ground  breed  Bufflehead  of  in  late  a l l nests  by p r e d a t o r s ,  and found  low b e c a u s e  tree  they  predators  due t o p r e d a t i o n  by K l a m b a c h ( 1 9 3 7 ) ,  that  experience  be  Ryder  i salso  almost  predation  season  6.8%  hatched  o f young  that  hypothesis  predation  exist  loss  i n t h e summer  Seasonal only  and  Thus,  success.  suggests  since  established  to  cold,  and  survival  of nest  Ducks  predation.  also  obs.).  Predation  Ruddy  were  (1947)  reproductive  Comparison and  (pers.  m o r t a l i t y of newly  to consider  determine  Nest  swimmers  to starvation,  High  Alley  necessary to  slower  comm.)  found  only  predation  may  and Coots,  t o experience  nest i n low nest  32  predation  except  are  common  nest  in cavities,  Becher's (J.P.  Nest  Savard  and  1972).  experienced because  pers.  other  mammalian  Barrow's  Goldeneye,  high  bears  nest preyed  which  predation upon  eggs  predators also  (31.6%) i n nest  in  boxes  comm.).  Flooding  loss  Ducks  than  Ruddy  nests  that  flooding  some a r e a s ;  were  they  (1974), Ruddy  Coot  found  studied  nest  were  flooding  found  appears  that  season.  no C o o t flooding  than  o f Ruddy  Duck  also  tended  to  were  i n marshes  and  occur nests  lost may  Tule  after were  9% o f and  loss  and  had nested.  flooded  common  McKnight  (1954)  due t o f l o o d i n g . be more  nests  than  nest Coots  Lake,  Duck  fewer  Collins Coot  cause  (1954) and  (1941),  found  studied  7% o f C o o t  at  few  loss in  t o be a m a j o r  Low  (1977)  Miller  Ruddy  suggests  nest  18% o f t h e Ruddy  whereas  (1960)  nests  literature  n o t seem  and Joyner  than  for  p a r k l a n d s ; however,  studying waterfowl  more  flooded.  greater  M i l l e r _ . and C o l l i n s  flooded,  (1974)  r e p o r t e d fewer  (1955)  (1960)  were  does  be  of the  cause  loss.  that  and Anderson  that  A survey  flooding  reported  to  i n the C h i l c o t i n  flooded.  however,  nests  appeared  i s a significant  Misterek  Rienecker  Coots  and Anderson  California that  to flooding  for  American  Rienecker  They  raccoons  (Fretwell,  Prairie,  Nest  of  where  and  Kiel  Thus, i t  later  i nthe  33  Nest  Desert ion  Comparison Ducks  had  Ducks  lower  deserted  predators (pers.  nest  nests,  or  significant  rather  Ruddy  than  a high  when  they  were  nests  were  deserted  1977;  Misterek,  1974),  Ducks, nest  Fredrickson,1969).  parasitism  explain  Coot  a n d Ruddy  hatch Ducks  may  young.  Joyner  to  deterioration  "rapid  parasitism. prior  probably  responded  intraspecific not  Prairie  fluctuations  in  nest  area  and Joyner  to the fluctuating parasitism. nest since  nest  nest  than  Ducks  and nests  15% o f (Joyner,  a l l  exhibit parasitic  rates  of  that  nest  depth"  cover"  seems  suggests  desertion  and  that  levels  Ruddy  did  a  "rapid  nests  than were Ducks  by i n c r e a s i n g  flooding  Ducks  was  rather  odd s i n c e  water  i n Ruddy  desertion  water  by Ruddy  successfully  parasitism  nest  Furthermore,  desertion  was  1972).  high  nesting  interpretation  to flooding,  explain  study  that  This  (There  are rarely  of p a i r s  studied  of s u i t a b l e  by  and t h e d i f f e r e n c e between  concluded  and l o s s  deserted  does  (1977)  Coots  Thus,  desertion  deserted  or Bufflehead  o f Ruddy  to  Gauthier  of deserted  and B u f f l e h e a d  i n the proportion  e x t e n s i v e l y , but  response  nest  Duck  nest  G.  (29.5%).  (Erskine,  p a r a s i t i s m whereas  Ruddy  nests  t e s t s . ) More  populations  (Weller,1959;  and  Goldeneye  Ruddy  because  lost  the frequency  Goldeneye  that  of nests  and Bufflehead  and B u f f l e h e a d  Barrow's  they  Savard  by c h i - s q u a r e d  i n other  to Coots  proportion  and Barrow's  compared  suggests  because  J.P.  (25.7%)  Duck  loss  relative  d i f f e r e n c e between  successful  facultative  success  found  Goldeneye  Ruddy  of nest  flooding.  comm.) a l s o  Barrow's no  of the causes  apparently  i n the Becher's not  occur  when  34  windstorms  occurred.  Similarly,  desertion  i n Barrow's Goldeneye  in  cavities.  tree  explanation  Cover,  of nest  Predator  Although vegetation, that  Ruddy  both  Ducks  when  Ravens  were  (when  Ruddy  than  Ruddy  as  Ducks  they  when  predation  than  have  nests  Coots.  predation  food be  nest  preferred  Possibly  nesting  were  nest  a more  of  better  less  Ruddy cover,  the period that  Coots  and the  cover  different.  i n the . season  to earlier  was  when  cover  nests  (when  late  nesting  Ducks  Duck  and caused  productive.  density, higher  (eg. insects nest,  but  density  less  i n t h e summer  nesting  such  several  suffer  predators  Also,  the  nested.  nests  available  Coots  in  considerably  Ruddy  Reduced  nesting  late  the total  Ruddy  to find  Ducks  during  emergent  not d i s t i n g u i s h between  why  f o r them.  in  significantly ponds  nested,  Nesting  nest  to destroy  Also,  I could  by Ravens  a v a i l a b l e when  they  the period  as compared  Coots  difficult  made  during  i n t h e summer  explanations  searching  nest  Fluctuations  Coots  near  not seen  results,  actively  seems  d i d not e x i s t  frequently  were  possible  made  and  nested  nested)  density  these  since  by t h e two s p e c i e s  did earlier.  the spring  nesting  chosen  species  less  and Ravens  From  Ducks  Level  as e x i s t e d  sites  each  found  parasitism  and Water  nested  available  during  nest  t h e same c o n d i t i o n s  The n e s t  season  and B u f f l e h e a d  explain  desertion.  Behavior  nested.  nested),  Thus,  f l o o d i n g cannot  density  other  may  to  stop  may  have  sources  of  as grasshoppers)  may  not  when  Coots  and a l t e r n a t e  nest.  sources  of  35  food  f o r Ravens  Ruddy  Duck  a l l interact  t o produce  reduced  predation of  unsuccessful  i n the f i r s t  nests.  Conclusions  1. A l t h o u g h nesting  30% o f A m e r i c a n  attempt,  contrast, nesting there  The  40%  may  be  a  advantage  and  of  summer.  Since  greater  earlier  attracted  to  average  significantly Various  visible Third,  time that  These  to nesting  nest  successfully. were  because  In  unsuccessful i n  results  late  predation This  indicate Ruddy  nests  density  then.  height  and  greater  later  that  Ducks  predators  density  have  than  upon  an  was s u p p o r t e d  by  maximum  destroyed  may  height  green when  Ruddy  visibility  nest  sites  chosen  and  i n spring  have  vegetation  s e l e c t e d by C o o t s  eggs  by  Ducks  was been  were nest.  of nests t o were  by Ruddy  slowly  in  of vegetation  sites  low  nests  emergent v e g e t a t i o n  to assess  flying  Coot  established  predators  of  be  were  nests  i n the season  nest  observed  and preying  Second,  might  American  spring  the  more  designed  that  more  a n d dummy in  i n the season, nests  in  i n summer  hypothesis  significantly  Duck  nest  Ravens were  vegetation  females  established  Ruddy  suggested to  Ruddy nests.  First,  measurements  predators  second  breeding.  nests  than  a  lower  late  results.  dummy  were  to renest.  that  predators  and  of  cost  time  I predicted  several  nested  d i dnot replace  insufficient 2.  most  Coots  over  more Ducks. marsh  b u t n o t i n summer.  36  3.  I  predicted that  be  an  advantage  summer wind  when  rainfall  and  results  did  could  than is  do also  might The  when  fewer  nests  Duck  Desertion  breeders  of  intraspecific  were  Ruddy nest  The  data,  spring  when  whether nest in the  only  loss  that  in  result  of  heavy  Although  a  long  to flooding  the  term  study  was  more  summer. rely  (Tome,  1981).  Since  Ruddy  Ducks  to desertion this  nest, than  less  rare  stored  would  have  energy  temperature  I predicted  b u t no C o o t may  on  ambient  hypothesis.  nests  parasitism, a  might  nested,  occur.  females  deserted  as a  Coots  Ruddy  Duck  showed  flooding occurred  the p r e d i c t i o n ,  d i d not support nests  t o f l o o d i n g i n summer  f l o o d i n g d i d not  than  higher  lose  in  not confirm  incubation,  results  Ruddy  subsequent  early  loss  breeding.  however,  in the spring  During  nest  Ducks n e s t e d ,  a c c u r a t e l y assess  common 4.  to late  Ruddy  storms;  lower  that  American Fifteen  nests  phenomenon  in  Coots.  percent  were  been  they  of  deserted.  caused Coots.  by  37  CHAPTER Feeding  Behavior  and  THREE  Survival  of  Ducklings  Introduction  For  north  Bufflehead arrive  and  at  American  the  early,  these  before  fall  delay  breeding  1981).  temperate  In  birds a  the Ruddy  April,  other  least  late  summer  species This  and  of  1)  than 7  the  ducklings  ducklings  grow  a to  to  In  after  c o n t r a s t , Ruddy  Ducks  (Gray,  in  they  research of  of  breeding  fledging  Ruddy  hatch  in  2)  until to  waterfowl  in  to  late  i n mid  other  the  fall.  answer  two  ducklings  species?  stage  breed  freeze  designed  rate  early  most  ponds  ground  rarely  ducklings  than  before  Tome, British  but  9 weeks  1980;  (southwestern  species,  later  breeding fledge  breeding  month  pairs  and  the  Ruddy  By  grow  at  Thus,  the  to  Goldeneye,  after  1980).  arrival  survival  reach  soon  young  parkland  on  Barrow's  occurs  the  south.  arrive  later.  as  (Bellrose,  for  more  waterfowl  focuses Is  or  Ducks  only  chapter  questions: that  more  time  Chilcotin  s i x weeks  breeding  migrate  month  such  grounds  species allow  Columbia),  at  Coot,  breeding  when  with  birds  similar  How  the  to  do  Ruddy  short  time  available? Because fledge,  low  breeding reproductive  Duck.  When  ponds  Ruddy  broods  reserves  to  females  tend  may  ensure to  late  affords less  success  might  freeze, ducklings not  have  successful abandon  be  that  fledged  for ducklings  predicted in hatched  or  migration.  broods  time  earlier  from  attained  the  Ruddy  the  last  sufficient  Furthermore, than  females  to  Ruddy of  other  38  species.  Even  particularly 1980).  maternal  females  early  found  be more  cover  Since whereas  danger  Ruddy  to  protective  more  spent  d u c k l i n g s have  s p e c i e s such weeks,  Ruddy  fledging  faster  than  the young  could  accomplished  ducklings  may  ducklings  Ruddy  toward  growth  bout  by and  may  broods  of  their  of  be  to  more dense  (pers.  comm.)  than  other  census  7 t o 9 weeks  Duck  time  rest  of e a r l y  i n dense  and  so f l e d g e  more  apparently  breeders.  and preen  species.  and  These  t h e amount  quickly  to  than  fledge,  and B u f f l e h e a d  mechanisms.  more  d u c k l i n g s t o maximize  i n which  Goldeneye  young  several  breeding  Second,  Ruddy  than  ducklings  feeding  to  ducklings. females  females  Savard  by t h e  grow  to  Rapid  growth  First,  Ruddy  swim  less  behaviors of energy  than would  directed  d u c k l i n g s of  early  species.  determine  or  feed  of e a r l y  enable  breeding  of  than  lead  P.  much  as Barrow's  14  be  J.  (Bellrose,  accompanied  survival  Ruddy  difficult  they  reported  of broods  Moreover,  ducklings,  view.  other  12  influence  i s imminent.  broods  Ruddy  always  o f p r e d a t o r s a n d may  s p e c i e s because  out of  may  of  has been  are almost  species.  Ruddy  waterfowl  a r e young,  protection  may  before  survival  broods  to the presence  cover  have  broods  breeding  alert  has  when  high  S i n c e young  female, Ruddy  so,  directly  ducklings of how  may  early much  gather  breeders. food  was  (time  taken  t o make a  dive duration  (time  spent  underwater)  of  food  gathered.  The  food per  While  collected  intensity  measurement  more  given were  I  did  i n each  number  of  possible  relationship  feeding not dive, dives) indirect  between  dive  39  duration since  or  feeding  ducklings  efficient Ruddy  at  likely  to  to  1973).  have body  be  ducklings  are  difficult  to  three  time  of  or  reared.  gathered  more  or  than  paddle  less  very  Thus,  size  food.  (area  and  tenuous  of  webbed  swimmers  in  the  unlikely  be  less  However,  therefore,  efficient  was  seem  f r e q u e n t l y may  abundant  it  may  finding  a l l waterfowl  was  feet)  they  are  (Raikow,  ponds  that  where  food  was  find. chapter,  I compare  Goldeneye,  categories: of  food  longer  largest  rather  (Barrow's  behavior  and  underwater,  the  food  this  species  dive  weight  more  Also,  In  that  swimming  Ducks  relative  intensity  budgets,  dive  Bufflehead  survival  ducklings.  of  and  Ducks and  young,  I measure  duration  Ruddy  time  to  American  behavior  budgets  feeding  early  of  of  intensity  breeding Coot)  in  females  and  females of  and  ducklings.  Methods  Determining  To  Age  of  estimate  survival  behavior  as  broods  according  directly;  Ducklings  ducklings  however,  broods  determined  (Larson given  and age  i t Often  information  Barrow's  Taber, class  age.  this  and  were  mature,  to  Bufflehead  rates  Goldeneye  according 1980).  were  at  to  and  control  was  necessary  age was  for  could  not  changes  to be  classify determined  available  for  broods.  Thus,  of  their  plumage  A l l ducklings approximately  ages  same  a l l these  development  classified the  in  within stage  a of  40  development mature  at  within  but  ducklings  different  an  age  of  rates.  class  different  Thus,  not  species  a l l  were  the  same  ducklings  was  assessed  are  ducklings  known  to  classified  c h r o n o l o g i c a l age  (see  Table  12).  Duckling  Survival  Survival In  the  and  age  that was  a  first class  J.  was  pond,  on  hatched.  that  the  The  and  chapter  2).  checked  was  used  survived  and  did  did  second  not  Goldeneye  Coots.  (Unhatched  the  by  the  in  between  was  1984.  nest  soon  A l l  a  hatching  based  on  data  information  location  as  methods.  and  brood  clutch  appeared  on  if  a l l  eggs,  had  remaining  in  the  brood  was  the  2B  age  to  compare  the  not  survive  to  and  Bufflehead  class.  A  chi-  of  Ruddy  age  class  ducklings  that  number the  2B  survive.  technique  of  different  determine  reached  test  difficulty  nest  young  ducklings  u l t i m a t e l y became  the  of  to  2  estimate  which As  by  ducklings  I collected for  Barrow's  of  This  broods  number  that of  and  was  contingency  survived  of  (see  nest  survival  assessed.  duckling  when  ducklings  that  was  Savard  The  recorded  with  2B  known  the  squared  technique,  P.  based  size  of  2B  estimated young.  assessing eggs  parents.)  and  egg  the  This  percentage  estimate  hatching shell  are  was  success quickly  of  eggs  made of  laid  because American  removed  from  41  T A B L E j_2 Comparison Goldeneye,  o f C h r o n o l o g i c a l Age ( i n d a y s ) of Ruddy, B a r r o w ' s and B u f f l e h e a d d u c k l i n g s f o r age c l a s s 1A t h r o u g h  MEAN  AGE  (IN  SPECIES  Ruddy  Duck  Barrow's  Goldeneye  Bufflehead  *-  +-  1A  1B  3  8  5  13  3  8  DAYS) FOR D U C K L I N G S AGE C L A S S;* 2A 2B 1C  IN  A  2C  GIVEN 2C  14  21  28  35  22  31  40  50  14  21  28  35  a s t a n d a r d c l a s s i f i c a t i o n s c h e m e f o r a g i n g d u c k l i n g s when h a t c h i n g d a t e s a r e unknown. The method i n v o l v e s i d e n t i f i c a t i o n of plumage c h a r a c t e r i s t i c s w h i c h change as ducklings develop ( L a r s o n and T a b e r , 1980). mean a g e e s t i m a t e s f r o m u n p u b l i s h e d D u c k s U n l i m i t e d R e p o r t (1983)  42  Female  Behavior  Behavior Bufflehead brood  was  ducklings  from  Behavior was  observed of  be  et  to  Ruddy  at  at  ten  least  females  test  to  the  Goldeneye A  and  female  swimming  out  or  of  resting,  with  a  The to  to  and be  i t s head  the  females  those  tests.  up.and  female of  alert  the  other  I also,used Ruddy  frequencies  'alert'  scope.  each  of  were  eyes  this  Ducks  that  out  when  of  were  spotting  frequencies  broods  (Ball  frequency  and  female  the  younger  predators  assess  intervals  hour.  with  to  in  considered  since  Bushnell  that  females  young  and  differed  were  behaviors,  contingency  sight  considered  To  compared  frequencies  Bufflehead  was  one  young  two  other  Goldeneye,  species  vulnerable  minute  were  chi-squared  were  more  through  s p e c i e s , by  broods  one  class  a l l  two  compare  these  a l . , 1983).  distance  for  Barrow's  how  class  with  may  recorded  Duck,  assess  with  relative a  was  behavior  one)  Talent  at  to  those  (class  behavior  observed  Ruddy  Females  a l . , 1975;  alert  female compared  defense.  separately  et  of  Barrow's  of  i t was  open,  and  sight. either  near  its  brood.  Time  budget  Time birds  of  ducklings  budget  through  a  duckling  broods  behavior  that  swimming,  and  of  ducklings  Bushnell was  were  assessed  spotting  recorded recorded  feeding.  was  Broods  every  observation  of  Behavior  of  Categories  of  telescope. ten  minutes.  included: of  by  age  class  resting, 1A,  1B,  preening, 1C,  2A,  2B,  43  and  2C  only in  a  were  observed  in each  others  of  the  same a g e  brood  tended  to  act  as  ducklings  not  considered  consisted equal  to  broods  were  hours.  one  observed  and  for  into  resting  ducklings  of  Since  each  was  class,  the  percentage  of  of  sight  of  in  the  not  Three  number  of  observer  was  observation whose  for  sum  heavily  more  were  fed,  brood  more  or  observed  behavior  the  duckling  categories  results  (The  compared  individuals  each  were  ones.)  brood  one  Thus,  behavior  were  most  duckling  broods  behavior.  out  each  small  class  ( i e . when  four  Large  age  a  class.  unit  the  and  each  age  independent.  (ie.  Within  feeding  be  a n a l y s i s than  converted  showed  to scores  in  a  fed), behavior  of  weighted  and  broods  with  all  was  and  different  at  least  added  together  observations  of  observations were  3  that  excluded  from  this calculation.)  Diving  duration  I  estimated  underwater taken Ruddy,  and  for  a  single  Barrow's that  marked  location  determined taken there  by  was  observation have  the  Shaun  dive)  duckling  to  were of  depth Boyd  and  feeding five  or  more  on  at  location  that  doubt  since  ducklings error  as  to  a  map  Wildlife to  were  which  duckling intensity  times  Bufflehead  feeding  (Canadian  dueklinqs  (time  and  dive  2 meters  some  contributed  of  duration  single  Goldeneye  ducklings the  intensity  diving  during a  feeding  by  other  the  from  Service). duckling  unmarked.  measurements  of  was This  time of  individual  ducklings.  pond  pond  (the  succession)  observing  from of  in  spends  and  depth  later  I I  profiles  Occasionally, the  one  under  problem  diving duration  may and  44  feeding  intensity;  nearest kept a  however,  neighbours  this  single  error  i n the  to a  duckling,  an  a  age  was  then  most  to  taken  age  median  a  to  durations  was of  dive  total  three  made  mean  diving  species.  Then,  the  the  numbers that  squared  median  duckling  dove  resurfaced  after  I  such  took  each  five brood  of  on  omitted.)  I  different  broods  the  age  brood  these  class.  For  studied.  A  diving  (Zar,  1984).  determined of  by  a l l three falling  ducklings.  t o g e t h e r and  a  of  durations  Ruddy  of  using  between  were  Goldeneye  of  These  compared  to  d u c k l i n g s by c h i -  age  on  stopwatch  the  dive.  Whenever  possible,  different  ducklings  of  broods  measurements and  compared  age to  a  duckling  (Insufficient  2C  when  same  class.  species-,  d u c k l i n g s were  the  when  fifth  intensity  each  started  taken  intensity  feeding  I  clock  the  each  particular  feeding  f o r Ruddy  for  many  by  s p e c i e s were  diving  as  average  ducklings  added  intensity,  completing  took  average  than  each  significant  for  Barrow's  stopped  a  The  class  more  tests.  samples,  available  Results  and  feeding and  age  were  For  for that  were  of  sample  i f differences  assessed  classes  Bufflehead  assess  of  probably  assessed  dives.  each  durations  was  contingency  To  species  number  f o r a l l age  of  of  surfacing  to  was  brood  d u r a t i o n s f o r each  plotting  above  broods  between  possible.  twenty  to determine  various  diving  as  synchrony  consisted  made  duration  of  and  brood  was  brood  for  diving  If a  represent that  classes,  test  Median  class, time  of  attempt  ducklings in.the  stopwatch  tendency  time  minimum.  different given  the  so on  these at  class  those  data  for  least  for were were two  (1A-2B). Barrow's  45  Goldeneye  and  Bufflehead  ducklings  by  a  median  test.  Results  Duckling  Survival  Comparison ducklings  of  have  three  species  Duck  eggs  higher  (see  laid  in  Fewer  Bufflehead  (22.6%,  nests)  became  age  class  was  Seventy-four young, and  young. Ruddy  Bufflehead  Female  became  nests)  of  do  2B  Ruddy  and  greater  Ruddy  the  of  other  young  American  i n Ruddy ducklings  of  Bufflehead tests  hatching than  to  that  of  the  of  Ruddy  nests  (29.2%,  (see  hatched  age  to  126 2B  f i g . • 4). became  Barrow's  that  were  nests),  hatching  showed  Barrow's  the  (31  hatchlings  2B  the  149  ducklings which  of  Coot  S u r v i v a l from  contingency  from  that  (26.9%,  s i x t y - t h r e e percent  percent  suggests  ducklings  Goldeneye  highest  only  ducklings  than  ducklings.  Chi-squared  significantly and  17 2B  young  T h i r t y - e i g h t percent  Barrow's  percent  thirty-three  3).  nests  also  whereas  of  survival  f i g .  examined).  eggs  survival  2B  Goldeneye became  2B  survival  of  class  Goldeneye  was  (p<.05)  (p<.00l).  Behavior  The  frequency  Goldeneye chi-squared  and  of  alert  Bufflehead  contingency  behavior  females  test  was  in  i s presented used  to  Ruddy,  Barrow's  in Table  13.  compare  the  The  frequency  46  to CO < -J (J  o to  _  o  _  10  Ul  to <  m  CM CO CD UJ o rr u.  n = 189  o  •fl-  n = 836  ea  n = 1378 n =137  o  < >  01  rr  o  _  o  -»  > 3 CO  RUOOY FIGURE 3_ : C o m p a r i s o n and  American  Coot  COOT  of Ruddy, Barrow's  total  number  BUFFLE Goldeneye,  s u r v i v a l from egg t o 2B age c l a s s  ( T h i s measure was c a l c u l a t e d the  BARROWS  o f young  by d i v i d i n g t h e t o t a l  which  survived  eggs  t o t h e 2B age  Bufflehead ducklings laid class)  by  47  CO CO  <  o  n=96  CO  n=588 o to  o  n=93  o  OJ  RU00Y  FIGURE  4  :  BARROWS  Comparison  Bufflehead duckling s u r v i v a l  of  Ruddy,  BUFFLE  Barrow's  from h a t c h i n g  Goldeneye  t o 2 B age c l a s s .  and  48  T A B L E 21 P r o p o r t i o n s o f O b s e r v a t i o n s Showing A l e r t Barrow's Goldeneye and B u f f l e h e a d females  PROPORTION SPECIES  Ruddy  FEMALES YOUNG  OF O B S E R V A T I O N S  WITH C L A S S ONE ( i e . 1a,1b,1c)  OF A L E R T  BEHAVIOR  F E M A L E S WITH C L A S S TWO YOUNG ( i e . 2 a , 2 b , 2 c )  (n=  59. 1 39 h r s )  51 .7 (n = 12 h r s )  (n=  67. 6 19 h r s )  65 .2 (n= 22 h r s )  (n=  70. 3 16 h r s )  61 .5 (n = 29 h r s )  Duck  Barrow's  B e h a v i o r i n Ruddy, w i t h Young  Goldeneye  Bufflehead  49  of  alert  females were  of  behavior  recorded  the other  two  found.  females  Alert  with  and  Bufflehead  the  incidence  (ie.  females  young),  no  The sight  of  one  females of  with  alert  significant proportion  the  or  with  class  one  Ducks,  Barrow's  with  the observer.  class  observer were  Goldeneye  and  of  15  ducklings.  2C  often  class  that  class  one  Also,  within with  females  Table  a  when  species  class  and  two  observations  that  out  with  Ruddy  sight  and  one  out  females of  however,  class  of  that  were  Ruddy  of  young;  between  out  Chi-squared  Bufflehead  showed  two  were  14.  of  often  females  Goldeneye  the  there  Barrow's  young  and  young.  Ducklings  presents for  Ruddy than  Barrow's  Ruddy  with  i n Ruddy  found.  in  more  differences  young.  females  were  were  Ruddy  with  two  that for  observed  compared  tests  females,  feeding  more  Bufflehead  females  was  Goldeneye  These  with  i n Barrow's  proportion  differences  Budget  Table  young  and  or  versus  significant  Bufflehead  Time  two  than  no  the  often  than  one  i s presented  female  of  young  observations  shows  sight  two  differences  tests  of  n o t more  young  females,  significant  was  class  contingency Ruddy  No  behavior  of  observer  Ruddy  species.  behavior  class  for  Ruddy,  Barrow's  ducklings  1A,  1B,  Goldeneye  ducklings  the p r o p o r t i o n  and  2B  were and  ducklings  of  observations  Goldeneye,  observed  2C  young;  of  however,  and  feeding  Bufflehead  of  and  1A,  Bufflehead and 2A,  the d i f f e r e n c e s  the other  two  resting  species  resting 2B,  and  between may  not  50  T A B L E J_4 Proportion Bufflehead  of O b s e r v a t i o n s Showing Ruddy, Females and Young Out o f S i g h t  PROPORTION  OF O B S E R V A T I O N S FEMALES  Ruddy  WHERE BIRDS  WITH C L A S S YOUNG  ONE  WERE OUT OF  FEMALES  35 .0 39 h r s )  (n =  16.7 12 h r s )  (n=  40 .4 19 h r s )  (n=  18.1 22 h r s )  (n=  33 .3 16 h r s )  (n =  Goldeneye  Bufflehead  SIGHT  WITH C L A S S YOUNG  (n=  Duck  Barrow's  Barrow's Goldeneye and of the Observer  7.5 29 h r s )  TWO  51  T A B L E 15 P r o p o r t i o n o f O b s e r v a t i o n s Showing R e s t i n g and F e e d i n g Ruddy, B a r r o w ' s G o l d e n e y e and B u f f l e h e a d D u c k l i n g s  P R O P O R T I O N OF O B S E R V A T I O N S SPECIES  TOTAL N (hrs)  OF  F E E D I N G OR  RESTING  1A  D U C K L I N G AGE C L A S S 1B 1C 2A  2B  2C  BEHAVIOR OVERALL AVERAGE  Barrow's Goldeneye  39  22.2  73.6  71.5  48.0  61.1  58.4  55.8  Ruddy  Duck  63  64.8  50.6  39.3  51.0  67.2  70.8  57.3  Bufflehead  47  24.6  37.9  55.5  54.0  56.5  61.0  48.1  52  reflect  real  spent  feeding  were  out  was  have  A  each to  sight  those  they  and  of  class of  the  Ruddy than  Barrow's  difference  i n pond  showed  intensity  that  other  two  16).  of  depth  be  each  the  actual  a l l three  species  when  they  same a s  what  frequency species,  of could  the  feeding  species.  median  (for  Ruddy  were  ducklings duckling  number each  (median  of  of  dives diving  species) longer  test,  There  l o c a t i o n s where  was  was  diving  p<.0l) no  and  obvious  diving duration  and  taken.  intensities  Bufflehead  from  for  significantly  p<.005).  intensity  different  compare the  feeding  and  observed  Goldeneye  at  Ducklings  species,  had  measurements  shows  was To  the  test,  Goldeneye  significantly the  Thus,  of  ducklings  not  I n t e n s i t y of  ducklings  (median  Barrow's  of  may  ducklings  two  above  Bufflehead  17  Table  other  compared.  Table  by  and  visible.  Feeding  (see  falling  feeding  unknown  were  ducklings  behavior  diving durations  durations  durations  The  time  equal.  range  age  was  resting,  Duration  broad  resting.  when  and  been  Diving  and  of  observed  feeding  d i f f e r e n c e s in the  of  feeding  of  1A  to  ducklings. Ruddy  A  2C  median  ducklings  intensity  of  Ruddy, test  was  ducklings  not of  53  T A B L E j_6 The Range o f A v e r a g e D i v i n g D u r a t i o n s O b s e r v e d f o r V a r i o u s Age C l a s s e s o f Ruddy, Barrow's G o l d e n e y e a n d B u f f l e h e a d D u c k l i n g s  SPECIES  (MINIMUM AND MAXIMUM V A L U E S FOR E A C H A G E 1A 1B 2B 1C 2A  CLASS) 2C  Ruddy  MINIMUM MAXIMUM  8.4 16.1  9.9 17.6  9.2 17.3  11.2 16.9  15.2 19.7  16.4 17.8  Barrows  MINIMUM MAXIMUM  3.6 4.4  5.6 13.0  10.6 15.0  8.6 11.2  15.2 19.5  14.3 16.8  Buffle  MINIMUM MAXIMUM  5.7 9.5  8.5 11.6  7.0 9.7  8.1 10.8  9.2 14.2  10.9 15.6  T A B L E 17 The Range o f A v e r a g e F e e d i n g I n t e n s i t i e s O b s e r v e d F o r V a r i o u s Age C l a s s e s o f Ruddy, Barrow's G o l d e n e y e a n d B u f f l e h e a d D u c k l i n g s  SPECIES  (MINIMUM AND MAXIMUM 1A 1B  VALUES 1C  FOR E A C H A G E 2A  CLASS) 2B  Ruddy  MINIMUM MAXIMUM  59.3 71.8  92.9 142.0  91 .6 109.7  119.1 138.5  130.8 1 39. 1  Barrows  MINIMUM MAXIMUM  76.5 78.0  69.2 94.3  31.1 132.6  102.5 1 26.3  121.5 185.5  Buffie  MINIMUM MAXIMUM  88.0 100.6  76.4 94.4  117.3 118.7  88.5 1 06. 1  91 .8 . 95.8  54  Discussion  Results higher  of t h i s  survival  Barrow's Libby  size  Joyner  (1976b)  the  duckling Gray  Ruddy  broods  of  found  in older  High result the  trend  alert  less  into  higher.  does  more  often  class  two  the  observer broods of  broods.  frequency and  than  Ruddy  the observer.  o f 2A  2A  bad  (2B  high  age  of  one  average weather  average survival studies.  class  (1977)  the size  1A a n d  Although  in other  of c l a s s  study,  Ruddy of  female  that  was  were  found 1A  that  broods.  d u c k l i n g s (no brood  size),  caused  high  why  Ruddy  were  Ruddy  one  a n d two  were  class  one  was  was  of the observer  only  observed for  of  were  between  sight  Barrow's  B u f f l e h e a d broods  broods  survival  difference out  were  Bufflehead.  led their  out of sight  to  Although  females  or  duckling  significant  broods that  Ruddy  females  result  not appear  Ducks.  Goldeneye Ruddy  no  Ruddy  significant,  Bufflehead, this There  d u c k l i n g s do  that  broods  the frequency  and c l a s s  84%  rates  Barrow's  not e x p l a i n  than  ducklings  Siegfried  were  of  frequency  Although  Coot.  found  had  d i d d u c k l i n g s of  size),  broods  while  not s t a t i s t i c a l l y  the  cover  rates  often  Similarly,  been  between  greater alertness was  than  ducklings  broods.  survival  from  have  duckling  of. h e r  2B  o f Ruddy brood  survival  Ruddy  American  1A  age c l a s s  high  year  and  50% o f  1A b r o o d s , 2B  that  class  survival  that  difference  i n one  mortality  low  found of  significant  age  ducklings  size  (1980)  although  to  approximately  for  suggest  Bufflehead,  found  rates  75%  rates  Goldeneye,  (1972)  brood  study  of the  Goldeneye  out of  sight  55  Several are  explanations  possible.  escape  F i r s t ,  predation mortality  season,  just  typical to  when  The  in  in  that  breeding  the  d i f f i c u l t  to  this  time,  so  the  of  absorb  able  reduce  duckling  in  warmer  required  Barrow's  to  Second,  earlier the  be  ducklings  waterfowl.  Third,  Ruddy,  Coots  which  successfully  the may  is  is  the  weather  mortality  to  explain  Goldeneye  a  and  (Females  cohesion may  have  of of  (see study  allowed than  is  duckling mortality  when  abandoned break fledged.)  to  2B  age  Ruddy Ducks ducklings  may  possible  of  sufficiently  ponds  freeze.  extensive larger in  success  Bufflehead The  18).  s l i g h t l y  suggest  reproductive  success  made  be  by When  class,  when  higher  broods down.  or  area,  early. is  to  Table  suggests  breeding  died  reproductive  breeding  which  as  high  it  have  s l i g h t l y  lower  have  high  of  population,  of  tends  survival  have  Caribou  is  successful  magnitude  that  consequence  radio-tagged  the  the  demonstrate  direct  as  be  mortality  incubated  a  not  can  success  but  do  survival  they  Goldeneye  in  thesis  duckling  some  Ruddy Ducks,  population  may  Ruddy better  higher  However,  brood  reproductive  American  be  most  be  would  of  f a l l .  disappear,  Estimates  Barrow's  this  determine in  boxes  of  without  freeze  than  survival  late  ponds  to  hatch  research  season.  Unfortunately,  high  of  predation.  Ruddy d u c k l i n g s  later  that  nest  may  may  in  ducklings.  of  ducklings  survival  young  predation  Further  results  survival  the  Ruddy d u c k l i n g s  differences Bufflehead  to  like  exposure.  high  Ruddy d u c k l i n g s  than  duckling  of  Goldeneye use  of  clutches  natural  and  nest to  be  cavities.  T A B L E J_8 R e p r o d u c t i v e S u c c e s s i n Ducks a n d C o o t s - The Average 2B A g e C l a s s Y o u n g P r o d u c e d p e r P a i r p e r Y e a r  SPECIES  Ruddy Duck American Coot Barrow's Goldeneye Bufflehead  CLUTCH S I Z E FOUND I N T H I S STUDY 6.10 6.63 9.77 8.05  Number o f  A V E R A G E 2B YOUNG S U R V I V I N G PER CLUTCH 2.29 1.93 2.62 1.82  57  (Bellrose Barrow's  (1980) Goldeneye  reproductive higher  than  cavities,  reported  7.6  studied  in  were  studies.  suggested  Time  This  further  of  be in  Budget  Time  of  south)  or  size  is  than  that  ducklings)  feed  that  because  adult  meters  and  ducklings;  the  from  populations  of  of  this  eggs;  Tome,  geographic Ruddy  parasitism higher  for' southern populations  Ducks  in  in  however  Ducks  other  northern  Lack  (1968)  populations  i f food  is  may most  Ducklings  suggest  of  to  Rule),  tree with  Ruddy  7.8-9.8  be  south.  Bufflehead  sight  that  than  generally  in  decline  higher  nest  may  normally  of  be  Thus,  study  due  higher  size  this  not  1975-  for  study).  nesting  may  northern  studies  interpret  be  size  clutch size  Joyner,  (Hesse's  budget  Goldeneye  to  (other  clutch  greater the  tends  in  does  Similarly,  clutch  this  Goldeneye  survival  size  the  in  populations  eggs;  birds  average  reported  difference  clutch  that  sometimes abundant  7  Clutch  populations  of  size.  1980-  lower  Barrow's  studies  eggs).  variation  of  that  clutch  in other  a  that  typical  assuming  (Gray,  1981-  than  success that  increasing  study  reports  broods  of  than  these  cover.  Bufflehead  Nelson  are  were  water  (1983)  and  class  and  difficult  (1976b) at  found  2  Barrow's  frequently  Siegfried  p r i m a r i l y i n open  vegetation.  Goldeneye  (especially  results  a l l species  in bulrush fed  Barrow's  ducklings  more  however,  Ducks  emergent  Ruddy,  Ruddy rest  observer  Ruddy  of  to  out  found  least that  of  2  Ruddy  58  Ducks  tended  Ruddy  broods  Ruddy  to  feed  more  often  broods  observer, broods  they  of  between  broods  most  of  Diving  Duration  occurred.  and  either  suggests  Barrow's  frequently  several  ways.  more  differences Ruddy  whereas  longer  near  to  distinguish  the  capture between  and  these  may  fed  noted  immediately a l l  duration  longer  of  than  ducklings  may  those  be  may  species  was  calories  feed.  chironomids  in  might  not  is  in  (food)  rapidly  by  reflect example, the  have  ducklings  research  less  interpreted  fledge  Goldeneye  of  longer  dive  For  Ruddy  Ruddy  Furthermore,  mean m o r e  explanations.  species  cover.  ducklings  Further  that  interactions  may  Third,  the  vegetation  diving durations  on  of  Ducklings  ducklings  where  when  sight  of  a l l three  results  Barrow's  surface. prey.  of  Thus,  feed  broods  Ruddy  Second,  have  to  Bufflehead.  dives  Ruddy  depth  might  Bufflehead  amphipods  These  intensively. between  tended  were  that  found  emergent  diving  intensity  longer  Thus,  of  (1972)  also  i n emergent  dives or  I  of  aggressive  I n t e n s i t y of  mean  feeding  First,  ducklings  spent  their  not  when also  out  enter  Possibly,  comparison  different.  collected.  feeding  they  that  do  since  significantly  cover.  Goldeneye  apparently  or  to  Libby  habitat.  vegetation  tended  They  Feeding  preliminary,  ducklings  are  species  time  and  extensively.  feeding,  the  water water  emergent  feed  emergent  rested  dives  two  after  leaving  A  not  deeper  i n deeper  i n the  may  these  immediately  after  are  in  mud, fed  may  required  on  take to  59  Conclusions  1.  The  young  of  American  2.  Results  Coot, of  hypothesis broods  o f Ruddy  Although  this  difference broods.  Similarly,  frequently  3.  females.  t o be m o r e with  than and  in  class  II  4.  Preliminary  Barrow's  support  suggested  resting  of  was  females  females  significant  with  than with  Goldeneye  .found  Bufflehead  no  broods  their  females.  were  than  the  class  were  one  n o t more  were  Barrow's  broods  were n o t  or  Bufflehead  or  more;  that  Ruddy  Barrow's however,  ducklings  Goldeneye  this  trend  may  grow  ducklings  was  only  by  evident  ducklings.  were  was  data  also  while  similar  of the other bout).  showed  significantly  the hypothesis  ducklings feeding  data  Goldeneye  sequence  young  cover  with  Barrow's  protective  two  cover  support  Bufflehead  there  Ruddy  than  Bufflehead  feeding  ducklings  bulrush  Also,  alert  or  in bulrush  females  those  broods.  Preliminary  faster  in  more  and B u f f l e h e a d  than  Bufflehead.  class  young,  Ruddy  observed  Goldeneye  females  two  b e t w e e n Ruddy  were  with  rates  unilaterally  Goldeneye  frequently  class  survival or  not  females  females  more  with  did  Barrow's  Ruddy  females  Goldeneye,  study  Ruddy  were  significantly  found  Barrow's  that  than  Ducks had h i g h e r  that  longer  the time for  that  a l l Ruddy  dive than  taken three  durations those  species. may  5  dives  These  grow  (by  gathering  more-  Nevertheless,  the  data  simply  or in  results  faster  species  may  Ruddy  of B u f f l e h e a d  to complete  ducklings  of  food-  than per  reflect  60  differences taken  to  i n the  capture  depth'where  prey.  each  species  fed  or  the  time  61  CHAPTER Seasonal  Abundance  of  FOUR  Food  f o r Ruddy  Ducklings  Introduct ion  Lack  (1954),  considered They  the  suggested  Moreau  (1950),  f a c t o r s which that  hatching  occurs  (Hereafter  this  birds  be  food called  research  on  for  ducklings  i s more  (1980),  Siegfried  (1973)  ducklings  and  Ruddy  crop  and  analyzed  (midge  Gray  ducklings  also and  approximately was lag  between  late Ruddy are  three  research  does high  ducklings  more  whether  i t  reproductive  is  not  habits  were  the  abundant  peak  when food  necessary success  of  density  eat  determine  Ruddy  late  Ducks.  the  larval in  in  hatch. when  whether food  the  Ruddy  occurred hatching  three  week  however,  ducklings the  because  If  Ruddy  of  that  Ruddy  influences  Gray  item  density;  chironomids  ducklings  density to  that  food  that  density  despite  chironomid  that  esophagus,  date  suggested  density,  demonstrate  Ruddy  hatching  chironomid She  the  collected  showed  peak  of  summer.  studies  peak  simply  Much  examining  most  that  abundant.  idea  the  have by  so  most  the  have  breeding.  breeding  is  in  of  Most  chironomid  may  abundant  determine breed,  of  food  others  timing  with  late  others  later.  and  and  hypothesis.)  and  chironomid  hatch  the  young  Lack's  the  that  weeks  with  peak  because  flies)  showed  for  abundant  their  (1972)  coordinate  is consistent  determined  coordinated  Gray's  Ducks  gizzard contents.  chironomids diet.  Ruddy  determine  typically  when  will  Fretwell  hatch  season.  chironomids  In  order Ruddy  food does  to  Ducks limits limit  62  reproductive  success,  food  and s e l e c t  density To  Ducks  assess breed,  1) What  do  ducklings  most  hatch?  3) Do  duckling  food  In  this  described measured density  this  female density  were  abundant  rearing  ponds  the  to  maximum  assess  food.  determines  when  on  questions:  three  2) I s  Ducks  food  summer  select  choice  to  the  ducklings  presented when  for  when  areas  densities  Ruddy  Ruddy  ducklings of  highest  of  choice  which  within  of  patterns by  of  Ruddy  invertebrates  hatched. feeding  ponds  The  area  and t h e c h o i c e those  is  invertebrates  consumed  ducklings  explored,  areas  ducklings  The s e a s o n a l  to estimate  maternal  and feeding  Ruddy  species  Ruddy  i s also  of  fed.  invertebrate  also  density  in  food  between  food  with  focus  eat?  females  for feeding?  where  are  areas  will  Ruddy  compared  in  Ruddy  f o r ducklings  late  chapter,  ducklings,  expect  ducklings  abundant  changes,  duckling  food  chapter  Ruddy  i n areas  relationship  would  the feeding  whether  and  most  we  of  and brood  by f e m a l e s i s  discussed.  Methods  To class  assess 1C  Appendix  to One)  immediately number recorded  food  habits  2C,  were  i n August  collected 1984.  and preserved  and taxa  of d u c k l i n g s , from  six ducklings, ponds  and the length  were  i n 70% i s o p r o p y l a l c o h o l .  of each  age  2 6 , 54 a n d 66 ( s e e  The d i g e s t i v e t r a c t s  of invertebrates contained  from  removed  Later,  i n the esophagi  i n v e r t e b r a t e measured  (+  the were or  63  0.5  mm).  Esophagus  soft-bodied  contents  invertebrates  contained  rapidly  digested,  contents  tend  to  underestimate  invertebrates  in  diet  for  each  assessments  which  0.5-1.0  cm.,  spanned 1-1.5  invertebrates  in  taxa 0.5  and  oven  each  size  the  average  dry  size  class  using  the  convention  54)  of  were  for  measured  the  Gerking  trap  samples  (4  diameter,  were had  taken  at  the  samples  l o c a t i o n on  total  animal  weights  1978)  of  pond  these  a particular was  presented that  three  were  1981)  dry  Ducklings  (breeding  where  10  invertebrates  for  each  cm.,  least  weight  from  at  size  0-0.5  except  ponds  (Kaminski,  each  crop  Dry  at  of  ducklings  Swanson,  and  soft-bodied  (ie.  information  these  after  are  establishing  drying  taken  Since  crop  in c a l c u l a t i o n s .  were of  by  a l . (1974)  volume  two day  modified  cm  et  data  on  diet  of  1970).  number  per  and  gizzard  length  The  total  weight  Swanson  habits  densities  class.  Duckling  substituted  Invertebrate and  taxa.  food  Bartonek,  determined  the  on  importance  etc.),  to  for  and  here.  gizzard  based  cm.  dryed  collected  diet  in  by  was  the  changes  divided  weight  in  presented  cm.  was  and  are  the  were  invertebrates give  of  (Swa n s o n  invertebrate  classes  only  ponds. ponds  26  collected:  10  and  15  lake.  core  Samples  feeding  ducklings  been c o l l e c t e d . To  determine  choice  of  at  ponds  two  each  of  mid-July suitable  feeding  the  the area  (breeding spring  and for  early  and  influence by  female  pond  68  summer  Ruddy  and  however,  Both one  invertebrate Ducks,  of  1983  ponds pond  was  density  samples  nonbreeding  months  August).  nesting;  of  pond  60),  (mid-May, had used  were  on  taken  once  in  mid-June,  emergent  cover  extensively  by  64  breeding rarely  Ruddy  Ducks  visited  Each  by  lake  ( b r e e d i n g pond  Ruddy was  Ducks  500 square  and  samples  On  10  core  the lake  with  quadrats  were  females.  Females  each of  month  feeding  sampled Ruddy  the  by  were  ( 6 A.M. females  t o 6 P.M. was  were  females  breeding  Ruddy  Ducks  and  were (pond  o f two  two  6 P.M.  the  60),  p o n d s were  c o m p a r e d by  of the  (pond  was  quadrats.  quadrat quadrat  the of  hour  t o 6 A.M.)  o f an  samples  68),  twelve  observed.  nonfeeding  trap  15- minute  the  and  each  the feeding behavior  at  in  observed  Ruddy  nonbreeding  and  other  quadrats,  Gerking  Ducks  for  recorded  feeding  Feeding  i n each  studying  observed  10  the  pond 6 0 ) .  twelve  Ruddy  invertebrates  females  random.  taken  breeding  chosen  into  meter area.  were  while  (nonbreeding  divided  approximately  68),  and  two Ruddy  sessions location  intervals.  I  where  most  feeding  where  the  fewest  pond  without  On  the  quadrats  were  quadrats  and  selected  at  breeding  and  t-tests.  Results  Food  o f Ruddy  Data Aggregate  on  occurrence divided  chironomids  duckling  weight,  invertebrates  item  Ducklings  and  (the by and  diet  aggregate  are  percent  seeds  are  number  of birds  t h e number seeds  summarized  compared. that  of b i r d s  o c c u r r e d most  in  and percent Estimates consume  Table  19.  occurrence of  of  percent  a particular  food  i n the sample) i n d i c a t e  that  frequently  i n Ruddy  duckling  T A B L E j_9 Foods o f Ruddy  Ducklings  ITEMS IN ESOPHAGI OF D U C K L I N G S  AGGREGATE PERCENT  AGGREGATE WEIGHT  PERCENT OCCURRENCE  Diptera: Chironomidae  49  91  50  23  5  33  9  2  17  1 18  t r a2c e  17 50  Odonata: Zygoptera Hemiptera: Corixidae Coleoptera: D yS te ie sd cs i d a e  66  diets  (50%  of  Measurements an  high. but  bird  was  show low,  foraged  in  Ruddy  weight  were the  (the  by  however,  this  with  important duckling  in  the  esophagi  contained  I  and  54  and  on  Ducklings  at  lake  fed  densities  of  particular dry  the  weight dry  to  one  larva. of  of  Zygoptera  Zygoptera  naiads,  diet  of  aggregate  item  consumed  food  items  invertebrates (91%);  esophagus  naiads only  food  the  a l l of  was  ducklings  in chironomids  While  each  for  in  d u c k l i n g whose  ducklings.  in  when  food  weight  i s concentrated  this 26  pond  54  on  a  ponds  with  diet  and  may two  of  four  ponds  fed  on  dytiscid 26  in areas  was  also  be  the  six  gizzards  comparison was  and  of  other  larva) 54  are  only,  while  seeds.  compared  diet  Table  invertebrates  and  also  ducklings.  the  (see  be  ducklings  of  because  different  can  where  contents  chironomids  variety  preference  esophagael  for this  these  corixids, on  duckling  i n v e r t e b r a t e sampling  comparing  ducklings  naiads,  total  due  about  from  pond  26  a  averaged  specifically  chironomids  of  naiads.  gathered  chose  of  diet  chironomids  measurements  contained  Information  feed,  with  of  by  Most  diet  weight  the  seeds  distorted  ducklings  chironomid  dry  of  chironomids  the  was  weight  these).  occupies  of  weight  result  item  importance  dry by  p r o p o r t i o n of  selected  along  be  a l l birds). of  not  contained  food  dry the  may  divided  esophagi  filled  The  total  a l l birds  were  (the  given  the  consumed  ducklings  consumed  be  that  a  whereas  mud.  esophagi  percent  which  P o s s i b l y , seeds rather  in  duckling  aggregate  a l l birds)  duckling  by  of  individual  over  of  the  those  of 20). at  (zygoptera  Invertebrate in  Table  21.  67  TABLE 2 0 Comparison of Dry Weight of I n v e r t e b r a t e s and Seeds i n t h e E s o p h a g i o f Ruddy D u c k l i n g s C o l l e c t e d a t Ponds 2 6 a n d 5 4  JAKE #  DUCKLING WEIGHT  26 26 26 54 54  540 285 240 155 1 40  SEX  AGE CLASS  MALE MALE MALE MALE MALE  2C 0 2B 0 2A-B 0 1C 0.0264 1C 0.2107  T A B L E 2_1_ Comparison of Average on P o n d s 2 6 a n d 5 4  Dry Weight  LAKE  INVERTEBRATE TAXA  DRY ZYGOP.  CHIRO.  MEAN  0.0104 0.0052 0 0 0  WEIGHT CORIX. 0 0.0063 0 0 0  of Invertebrate  54 9 5 % C.l  DYTIS. 0.0009 0 0 0 0  Taxa  LAKE MEAN  SEEDS 0.0001 0 0.0020 0 0  p e r Sample  26 9 5 % C.I  Crustacea: Amphipoda  0.8800  0.5300  0.4320  0.3500  Hemiptera: Corixidae  0.0121  0.0131  0.0506  0.0338  Coleoptera: Dytiscidae  0.0019  0.0019  0.0005  0.0005  Odonata: Zygoptera  0.0019  0.0021  0.0095  0.0081  Diptera:* Chi ronomidae  0.0007  0.0013  0.0320  0.0378  Diptera:** Chi ronomidae  0.0223  0.0105  0.0113  0.0041  *-mean **-mean  d r y weight dry weight  estimates estimates  from from  modified Gerking core samples  trap  samples  68  Amphipods  were  invertebrate, collected column  on  lower it  on  was  pond on  on  Seasonal  54,  pond  5  from  quadrats  were  density  where  Density  and  than  of  Ruddy  Ruddy  month.  highest  of  Patches  are  simply  Chironomid  i n August,  column  chironomid  Ruddy It  was  although,  the  surface)  was  chironomids,  than  avoided.  larva  However,  in core  samples)  the was  breeding  and  least  density  as  i n the  Ruddy  zygoptera  (see  in this  water  broods  5C)  'Food  for  column  in  the  a  (Fig.  the  ( F i g 5B)  in  Two  section,  replicates  density  (Fig.  68...  invertebrate  often  Ponds');  treated  zygoptera  pond  i n f o r m a t i o n on  within  density  and  study in  mud  the was  May. one  broods also  water  gather  in chironomid  when m o s t  contrast,  the  Zygoptera  on  f e d most  water  Only  August  females  In  in  changes  provide  hatched. and  and  to  Choice  in  ducklings  26.  Chironomidae  sampled  were  of  other  which  near  (as measured  pond  through  density  pupae  any  diet  d u c k l i n g s f e d on  mud  on  than  i n the  samples  chironomids  area  highest  and  compares, t h e May  appear  Gerking  i n the  quadrats  particular was  54  abundant  Chironomid  in  where  Abundance  densities  5A)  26  density  two  pond.  where  more  d i d not  macrophytes  pond  Figure  the  these  measured with  chironomid higher  yet either  (as  associated  considerably  brood  typical reared  when  was of  the  reared study  successfully  the  ducklings  on  this  area, (3 were  pond  in  i t hatched  out  of  young,  5  1983.  Unlike  in late  young  June.  fledged)  chironomids,  and  DRY WT. OF CHIRONOMIO LARVA PER GERKING SAMPLE-BREEOING PONO (g) 0.05  0.10  0.1S  0.20  I  +i  IJ^IIIIIIIIIIIIIIIIIIIJIIIIIIIIIIIIIIIIIIIIIIII »-»  ree 0.  tn rr  19 a.  0> rr Ul  l-« 0)  o g  rr  C rr  n •rf*  tn O 3  rere O 3 re U3  MI  >Q C 01 CL Ol rr  in CB rr  tr  SB  c a a s. MI  ( i» 5 •  1  Ml re A re a. a  9  3  O  •oo  cn rt ft n  di  . CD U  n 3" O 3 O  9 a.  a  M.  !-»•  cn  3 O 3 Ml  Ml  >  —  .Q C  cv a o > rr cn Di rr  tr  »  c a a •<  •<  U3 O  •o rr  iO  C  01  a ri DI  rer r re3 U l 9 Ml  CD l-» l» tn  r-l 01  01 01  a  01 rr  tr M.  ••J  *-* CI  a c o o pi » a TJ9 l o i  iO  n  M DI rr  cn  "I  w c a. a •< Ml  h-»  01  n <  01 t-"  o zr M«  re 9 01 I-  1  ri  o 3  re Ul  Mi  o 9  •—•  o o 3  Ml M«  a.  re 3  n re  0RY MT. OF ZYGOPTERA LARVA PER GERKING SAMPLE-BREEDING PONO (g) °-°  0-1  0.2  0.3  —'  M>  1  0.4 1  0.5 I  3 rr  re •I  —I o>  <  DI I— Ul  1  M.  Q.  oo »— • re rr  ui  *-»• 3  n  3  a a* OD  9  •o I—  19  o cn rr  Ml  »-•• 3  a >o •Q c  yr  re IB 3  3  .  tQ  »— •o o  ft  CA  DI  a  n 01 rr tn  Ut  -  o Ml  ca 3 a  3 lO Ul 01  9  •o  re tn o Ml  3  a cr* CO »->• 3 —• VO CO u>  rr  Ul  •**»• Mi  rr  !-«•  ro  ev —-*•  re re tn re a .  3 vO iO  c  DI  a. 01 rr CA •—'  3  n vr H' 3 lO Ul 01  9  01 3  a.  •o  DRY WT. OF CHIRONOMID LARVA PER CORE SAMPLE-BREEOING PONO (g)  r—  re cn  0.0  M-  69  o  01  3" O Ul re 3 re a o reffl re 1 3 a a. _r O **• 3 Ml 3 » i O re re I D ia reMl N  reU 3 tocnQ> CD LO a  a 3  C  9  "8  It 01 Ul rr  o  Ml 01 a re re re it Q. re re re 3 a a a a. re 9 Ul re 3 3 3 a . to 9 o re CO lO rr IA 3 Ul  x> c  n DI rf CA •v.  ar r in  »v  •->  ge  lO  MI  n  or  ro »*• 3 3  <  3 O 3  HI  ae  3  a o>  r— U n  re cn  ta  e n tna a n o  pa  3 O 3  CL  f i  O.00S  0.010 '  0.015 1 —  0.020 l  4-i  70  zygoptera  densities  were  low  relative  to  those  in  May  and  August.  Food  Density  and  Figure  5  zygoptera  Choice  also  in areas  of  Patches  compares  where  (nonfeeding  quadrats).  these  chironomids  tended  nonfeeding be  quadrats,  higher  in  Significant  quadrats  samples  density P<.001).  No  densities but  were  observed  and  Figure  6  larva  and  density breeding  of  presents  zygoptera  nonbreeding  pond these  pond  of  60.  density  of  August,  June,  in  density  nonfeeding  than  in  tended  to  quadrats.  feeding  chironomid  density  measured  and  samples  July  and  (t-test;  differences  July  in  f e e d i n g and tended  to  August  by  chironomid  p<0.0l,  August  zygoptera nonfeeding be  and  naiad  quadrats,  slightly  higher.  Ponds  the  changes  naiads  from  Comparison  invertebrates 68.  and  between  between  Choice  and  and  quadrats)  observed  in feeding quadrats  density  chironomids  (feeding  and  than  p<0.05),  Gerking  of  in feeding quadrats  i n May  were  significant  densities  Food  by  lower  in August  (t-test;  measured  be  density  July  quadrats  differences  nonfeeding core  to  Ponds  f e d most  In  whereas  feeding  the  females  least  within  Zygoptera  was  in densities May  of on  through  Figures  5 and  average  density  of  in both  much  chironomid August  6  shows higher  quadrats  at  on that at the  DRY HT. OF CHIRONOMIO LARVA PER GERKING SAMPLE-N0N8REE0ING POND (g) 0.0  o 3 tr  rt C  o .a « c 01 re re a 3  tO  •o o 3 a a* o  3 . OD UJ  Q> rt  in  UI QI  3  •a  n  3 O 3 tr »n  * o .O c 01 re a re a »*• 01 3 rt  o o  •6 o> n M> U)  O 3 o rt.  lO  in  •a o 3 a  cn 01 3  l-»  re a a. 3 01  •o 0 3 a  <: 01 t->  o 3n  O 3 O 3  a a ti re 3 t-« re •n a  »<  e  tn  UI  rr  n  VI rt a M-  tr  s:  50 c a a •  c o VI  3  O O t|  re  in 3 •o i-» 01  re  UI  o  ft  o  3 —»  O0 W  Tt—' >  a  —•  3 O 3 tr  n o 3 •01o  3  •v 0  3 a 0)  i  w  c a Cb  ><  •O  c a  lO  n. 01  N  •a o 3 a.  •<  tr. o  3 re 01  —•  IO  3 01  aj LJ  M> 01  a a re 3 UI  re  ID  3 re a lO tr re  •<  C  o  3 O rn  re r t c UI  rt  0>  re lO a O H.. •rot 3  01  wi  o re re a M>  n  VI  O  H.  *• 3  lO  VI 01  3 •o >—  rt  in  tn  re  UI  o  Ml  n  o 3 •01o n  in o  3 O Mi t-» 01  in o> 3 •o *-*  n. < 01 »-• o  M-  o 3  re a. 33  0>  •o o 3 a n n n t-> 01  ><  O 3  0.20  »-*  Cl a w IT.  3n  7  DRY HT. OF ZYGOPTERA LARVA PER GERKING SAMPLE-N0N8REE0 ING P0NO (g)  oo »-••  0.0  0.1  0.2  0.3  0.4  0.5  I  I  I  I  1  I  3H  a  n D rf n < r-« tA  CJ a a rn re VO 3  in rt  Ui  <#>  re in  c U)  3 reU3 a tr re  » c a a ><  1  o c n  >  —  0. 15  0.05  o c o  ?r in  DRY WT. OF CHIRONOMID LARVA PER CORE POND (g)  3  lO.  0.0  in 01 3  SAMPLE-NONBREEDING  0.005  0.010  0.015  0.020  I  l  I  I  •o  re in z  O  TL  72  nonbreeding quadrats  pond  at  ,p<0.05).  the  the  breeding  lower  breeding  density  in  the  chironomid  density of  the  breeding  was  the  were  the  mud  was  (t-tests;  pond  that  water  pond; at  pond.  two  For  in the  was  quadrats  chironomid  ponds.  larger  Where density  example,  significantly than  (t-tests;  between  the  both  column  however,  the  in  months  comparisons  observed  nonbreeding in  the  similar  nonbreeding  pond  in  of  than  for a l l four  nonbreeding  differences at  quadrats  i n most  mud  occurred  lower  pond  density  and  the  significant  the  significantly  Chironomid  significantly of  was  August  greater  in  both  feeding quadrat  of  p<0.00l).  Discussion  Food  and  of  Ruddy  Ducklings  Chironomid  larva  were  also  most  commonly  occurring  ducklings  collected  the  esophagi appeared  of to  Ruddy be  the  most  both  consumed  important  ducklings  sampled.  Zygoptera  importance  since  represented  contained  in  naiads six  were  food  duckling  item.  naiads  collected. occurs,  in this  were 5%  of  however,  digestive  Thus,  these  only  greatest  biomass  invertebrate  component  naiads  esophagi;  d i s c o v e r e d i n the  ducklings  zygoptera  they  i n the  in  perhaps  of  i n l a k e s where may  and  of  biomass zygoptera  four  be  Ruddy  secondary  of  high  the thus  of  total  traces  tracts  invertebrates  study diet  the  in  of  density the  the of  staple  73  Cottam (1973)  (1939),  also  found  ducklings. common found  Both  Siegfried  i n the gut contents corixids  been  (Tome,  1981),  they  Seasonal  Ruddy  in  these  invertebrates  Lack's  chronology  ducklings  eat  would  i s given  Zypoptera  naiads  and chironomid  chironomid  larva  While  i s  chironomids, straining, to pond  54 w h e r e  My  were  Cottam  zygoptera Ruddy  Ducks  important  item  Cottam  that  of feeding that  chironomids Ruddy  of these  would  showed  was  Ruddy  invertebrates  July  or  only  on  highest  in  in  was  of late  August.  chironomid'  on  these  better at  more  Furthermore,  column  early  the d e n s i t y of  d u c k l i n g s were  i n t h e water  that  density  be h i g h e s t  of  hatch.  and suggests  that  he s u g g e s t e d  fed  ducklings  ducklings can exploit  i n t h e mud.  ducklings  that  and chironomid the density  late  predicts  column  reported that  Four  in  larva  Ruddy  that  when R u d d y  hatch  results  naiads  predicts  hypothesis  i n t h e water  possible  a mode  capturing  density  Ruddy  Zygoptera  i n Appendix  Lack's  i t  only  of adult  a s an  zygoptera  i n the Chilcotin  August.  and  be h i g h e s t  Thus,  and  of  Although  diet  observed  Siegfried  amphipods  ducklings, while  the  hypothesis  August.  July  and  staple  found  ducklings.  not been  ducklings  primarily,  most  main  Cottam  of Chironomidae  larva  Nesting  of  (1963)  diet.  Abundance  If  t o be t h e  o f Ruddy  reported have  Collias  and  i n the diet  have  duckling  and  chironomids  naiads  in  Collias  suited breeding  larva  only,  was v e r y l o w ,  74  whereas fed  on  that  in cores  chironomids  was  i n the  data  invertebrate densities  chronology  did  ducklings though at  was  Although  this  brood  show  have  to  that  are  Density  was  were  other fed.  Choice  fed  in the  larva for  food  and  of  A on  May the  habits  brood  not with  this  to  within  Ponds  Ruddy  pond,  even  naiads  were  period.  population,  Ruddy  and  of  August  Ruddy  larva  rearing  brood  zygoptera  the  is  fed.  the  successfully,  of  most  choice to  than  factor we  Patches  densities  the  chironomid  Since  ducklings  successfully  chironomid  not  females  do  zygoptera  densities  in nonfeeding besides do  not  food know  (feeding  and  a  i t not  naiad  for  food  feeding  what  naiad  density (and  might  more  suggested  where  females  lower  and  (where density have  samples  difference).  This  determined  although  quadrats  significantly  quadrats.  quadrats  quadrats),,  Since  statistical were  i n the  nonfeeding  quadrat,  patches  establish  greater  significant.  feeding of  were  often  feeding  l e a s t ) were  necessary  quadrats  duckling  68,  ducklings  hypothesis  hypothesis.  typical  reproduce  between  higher  larval  not  naiad  females  determined  was  Lack  that  highest.  Zygoptera  fed  fledged  the  pond  Lack's  measured  when  and  differences  and  suggesting  of  where  breeding  chironomid  to  breed  densities  females  of  point  comparison  support  reared  low  does  where  the  not  densities  the  Food  on  high, Thus,  supported  Finally,  the  mud.  clearly on  by  very  However, in  feeding  that  some  and  young  ducklings  were  females  75  feeding  on  Chironomid 68  were  i t  larva  was  suggested  Food  and  where  prediction pond  68  column lower  of  main  was  partly  was  not by  density. success  including  limited  the  high  several  conclusions. extensively numbers  of  food  When by  and  ducks  of  result  been  reared  core  August,  the  indicate  that  that  pond  reproductive  unknown  factor  nonbreeding A  larger  produced  studied  invertebrate  in  be  limited  there.  used,  to  invertebrate  the  have  water  by  some  using  might  the  therefore,  have  breeding  density  may  on  This  tended  and  governed  (1980)  and  larva  in July  c h o i c e , but  rarely  highest.  in  in  breed  comparing  results  density  important should  was  data  and  still  avoid  3  Ducks  chironomid  These  may  Joyner  invertebrates  diet  .  densities  ponds  not  ponds,  and  pond  This  are  chironomid  ponds  chironomid more  the  since  was  pond to  naiads  Ruddy  However,  females  Ducks  by  60,  these  influenced Ruddy  pond  rearing.  on  where  54).  zygoptera  results.  breeding  c o u l d have  invertebrates  nonbreeding  Alternately, and  hatch,  ponds.  on  or  on  ponds  and  68  zygoptera  naiads  brood  Ruddy  caused  despite  higher  26  lake  supported  nonbreeding  for  and  these  zygoptera  time  choice  have  of  densities  these  Ponds  ducklings  in nonbreeding  samples  food  with  of  larva  density is  on  interpret  breeding  chironomids  Choice  when  of  ( b r e e d i n g pond  either  chironomid  to  naiad  those  ducklings  on  determining  zygoptera  than  that  Density  difficult  sampled  successfully  ponds  and  higher  ducklings  If  is  he taxa  4 found were  may pond  sample,  different ponds that  used the  positively  76  correlated  w i t h duck u s e o f p o n d s .  Conclusions  1. C h i r o n o m i d components 2. R e s u l t s Ruddy  of  this  zygoptera  greater  First,  naiads  were  of d u c k l i n g s c o l l e c t e d study  do  densities  Second, d e n s i t i e s  were s i g n i f i c a n t l y they  were  chironomid densities  measured  ducklings  tended  had  hatched  of l a r v a l c h i r o n o m i d s  l e s s when d u c k l i n g s were before  study.  when  ( J u l y a n d A u g u s t ) were n o t s i g n i f i c a n t l y  than t h o s e measured b e f o r e d u c k l i n g s  June).  in this  major  i s most a b u n d a n t f o r t h r e e  zygoptera naiad  were p r e s e n t  the  not support the hypothesis that  D u c k s b r e e d when f o o d f o r y o u n g  ducklings  than  and  i n esophagi  main r e a s o n s .  and  larva  hatched  t o be l o w e r  in  present  i n t h e mud in  " i n May. areas  where  Ruddy D u c k s a n d young f e d t h a n i n a r e a s t h e y a v o i d e d .  (May  August Finally, female  77  CHAPTER General  In  this  potentially focusing nest of  on  food  not  Ruddy  At breeding  nest breeds  Second,  than  found  more  Ruddy does  As Ducks,  upon  the  Ducks  against  well this  nests near  ponds  late  that early  study  this  do  may b e a n  suggests  reasons  not explain  why  an advantage  of  in  nests  f o r Ruddy was  than  an advantage  by Ruddy  nest  which Ducks.  significantly  Finally,  spring  First,  (a s p e c i e s  Ravens  b u t n o t i n summer  heavy  than i n  conclusion.  than  predation  advantages  i n summer  Coots  nests.  to avoid  breeding  focuses  dummy  of such  nest  as examining  predation  i s lower  greater  i n spring  existence  breed  indicate  deterrent  support  dummy  abundance  f o r young  but does  f o r American  o f summer  include  breeders.  predation  spring  than  a v a i l a b i l i t y of  of food  in the Chilcotin,  was s i g n i f i c a n t l y  often  Establishing  nest  late  and  that  but nest  late  Ducks  predation  that  preying  t o become  of  vegetation,  suggest  that  rather  I consider  information  t o breed  observations  predation  greater seen  to  early)  This  of factors  breeding,  and abundance  factor.  i s that  Several  loss  results  breeding,  f o r Ruddy  range  Factors  of green  delay  continue  evolved  late  spring.  My  a of  hypothesis.  f o rnests  Ducks  least  timing  availability  delaying  Ducks  investigate  single  vegetation  Ruddy  Discussion  the  f o r young.  important  it  a  significantly  why  I  influence  predation,  green  that  study,  FIVE  in does  were  a n d were summer. not prove  predation,  i n the spring  but  may b e a  Ducks.  of late  on c h a r a c t e r i s t i c s  breeding  in  o f Ruddy  Ducks  Ruddy that  78  enhance Ruddy of  their  ducklings  early  frequent more  may  body  weight  (1968)  food  for  rearing area  growth is  allow  Ruddy  may  factors  adult  that  is in  does  that  short  not  less  than  of  growth  young  are  larger  supply.  likely  to  grow  considered  the  to  appear  ducklings  Second,  ducklings  eggs  more  caloric  to that  is  a  large  egg  required  at  of rate  size  to  (Lack,  a  larger  breeding  ducks.  conditions  where  shortage  problem  egg  anatidae  early  this  feeding  of  hatch  in  Food  be  the  in  content  on  ratio  in  ducklings and  research  largest  First,  durations,  not  and  than  Further  i s the  weight  suggests young  rates.  Ruddy  rapidly dive  other  Ducks  i t seems more  ensures  more  successfully.  Longer  necessary.  allow  period  and  resting  i n Ruddy  of  fledge  late  assimilation efficiency  I t may  fraction  breeding  species.  and  affect  nutrition  Lack  to  able  however,  as  and  1968).  are  feeding  such  food,  to  breeding  quickly;  study,  ability  in  size  in  the  the  Chilcotin  i n Ruddy  between  brood  Ducks  hatching  and  fledging. Various  features  unsuccessful  i f they  eggs  drab  of  American well and  a  Coot,  with are  not  females  do  by  predators  vicinity I  of have  bred  cover have but  down  coots  (Ryder,  analyzed  the  suggest Most  them  brown Ruddy  or  that  with  down  speckled Duck  which  the  they  would  be  and  coots  lay  waterfowl  eggs  vegetation.  a g g r e s s i v e l y defend  unlike nests  and  vegetation by  Ducks  earlier.  example,  covered not  Ruddy  colour  for  the  of  nest  or  vegetation.  eggs are  that  blend  bright  white  Moreover, against  Ruddy  intrusions  defend  territories  of  determines  in  the  1959). question  what  timing  of  79  breeding  i n Ruddy  breeding  late.  direct like  effect  egg s i z e  ensuring freeze. and  that  attempted  Factors on  and suggested such  and d u c k l i n g ducklings  that  i n Ruddy Ruddy  to breed  Ducks Ducks  earlier.  have  (eg. d u l l would  be  predation  while  an  sufficiently  appropriate  of the advantages to  nest  success,  behavior  grow  some  as reduced  reproductive  Characteristics  not found  suggest  Ducks,  to fledge  eggs less  a  characteristics  indirect  to early  have  effect before  breeding  covered  with  successful  by  ponds  species down) i f they  80  REFERENCES CITED  Alley,  R. a n d H. 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C r i t e r i a o f S e x a n d A g e . F o u r t h e d . W i l d l i f e Management T e c h n i q u e s M a n u a l . The W i l d l i f e S o c i e t y . W a s h i n g t o n . 143-202 pp.  In  Libby,  to pp.  Low,  H.J. marsh  1972. Ruddy Duck b r o o d d i s t r i b u t i o n i n r e l a t i o n h a b i t a t . M.S. t h e s i s . U n i v . W i s e . ( M a d i s o n ) . 59  J.B. 1941. 517.  Nesting  of  the  Ruddy  Duck  i n I o w a . Auk  58:  506-  83  M c K n i g h t , D.E. 1974. D r y - l a n d n e s t i n g by R e d h e a d s D u c k s . J . W i l d l . Manage. 38: 112-119.  and  Ruddy  M i l l e r , A.W. a n d B.D. C o l l i n s . 1 9 5 4 . A n e s t i n g s t u d y o f d u c k s a n d c o o t s on T u l e L a k e a n d Lower K l a m a t h N a t i o n a l W i l d l i f e R e f u g e s . C a l i f . F i s h a n d Game 4 0 : 1 7 - 3 7 .  M i s t e r e k , D. L . 1 9 7 4 . T h e b r e e d i n g e c o l o g y o f t h e R u d d y D u c k ( O x y u r a j a m a i c e n s i s ) on R u s h L a k e , W i n n e b a g o C o u n t y , W i s c o n s i n . M.S. t h e s i s . U n i v . W i s e . ( O s h k o s h ) . 82 p p .  M o r e a u , R.E. 1950. The 92: 2 2 3 - 2 6 7 .  breeding  seasons  of A f r i c a n b i r d s .  Munro,  J . A . 1945. The b i r d s o f t h e C a r i b o o P a r k l a n d s , C o l u m b i a . C a n . J . R e s . (D.) 23: 17-103.  Nagel,  R . E . 1 9 6 9 . P r e d a t i o n on c a v i t y a b u n d a n c e i n wood t h e s i s . Iowa S t a t e U n i v .  M.M. 1954. P r o b l e m s o f american b i r d s . Condor  British  eggs i n s i m u l a t e d n e s t s and d u c k n e s t i n g h a b i t a t . M.S. ( A m e s ) . 94 p p .  N e l s o n , C. 1 9 8 3 . U n p u b l i s h e d abstracts Conference, Summer 1 9 8 3 .  Nice,  Ibis  of D e l t a  incubation periods 56: 173-197.  tree  Waterfowl  in  north  Perrins, CM. 1965. P o p u l a t i o n f l u c t u a t i o n s a n d c l u t c h - s i z e i n the G r e a t T i t , P a r i s major . J . Anim. E c o l . 34:601-647.  . 1 9 6 6 . S u r v i v a l o f y o u n g Manx S h e a r w a t e r s P u f f i n u s p u f f i n u s i n r e l a t i o n t o t h e i r presumed date of h a t c h i n g . I b i s 108: 132-135.  112:  . 1970. The 242-255.  P i c o z z i , N. 1 9 7 5 . Manage. 39:  timing  of b i r d s '  Crow p r e d a t i o n 151-155.  breeding  on m a r k e d  nests.  seasons.  J.  Wildl.  Ibis  84  Raikow, R . J . 1973. L o c o m o t o r mechanism W i l s o n B u l l . 85: 295-307.  Ryder,  i n North  R.A. 1 9 5 9 . I n t e r s p e c i f i c i n t o l e r a n c e i n U t a h . Auk 76: 4 2 4 - 4 4 2 .  . 1961. Coot a n d duck T r a n s . N o r t h Amer. W i l d l .  American  ducks.  of t h e American  productivity i n northern C o n f . 26: 134-147.  Coot  Utah,  R i e n e c k e r , W.C. a n d W. A n d e r s o n . 1 9 6 0 . A w a t e r f o w l n e s t i n g s t u d y on T u l e L a k e a n d L o w e r K l a m a t h N a t i o n a l W i l d l i f e R e f u g e s , 1 9 5 7 . C a l i f . F i s h a n d Game 4 6 : 4 8 1 - 5 0 6 .  S c h r a n k , B.W. 1 9 7 2 . W a t e r f o w l n e s t c o v e r a n d some r e l a t i o n s h i p s . J . W i l d l . M a n a g e . 3: 9 2 - 9 8 .  predation  S c u d d e r , G.E.E. 1969. The f a u n a o f s a l i n e l a k e s on t h e F r a s e r P l a t e a u . V e r h . I n t e r n a t . V e r e i n . L i m n o l . 17: 430-439.  S c u d d e r , G . E . E . a n d K.H. M a n n . 1 9 6 8 . T h e l e e c h e s o f some in the Southern I n t e r i o r Plateau region of B r i t i s h C o l u m b i a . S y e s i s 1: 2 0 3 - 2 0 9 .  lakes  S i e g f r i e d , W.R. 1 9 7 3 . Summer f o o d a n d f e e d i n g o f t h e R u d d y i n M a n i t o b a . C a n . J . Z o o l . 51: 1293-1297.  Ruddy  diving 736.  Ducks.  the  . 1976a. B r e e d i n g b i o l o g y a n d p a r a s i t i s m Duck. W i l s o n B u l l . 88: 566-574.  Duck  i nthe  . 1976b. S e g r e g a t i o n i n f e e d i n g b e h a v i o r o f f o u r d u c k s i n s o u t h e r n M a n i t o b a . C a n . J . Z o o l . 5 4 : 730-  . 1976c. I n c u b a t i o n b e h a v i o r o f Ruddy Condor 78: 512-517.  . 1977. N o t e s on b e h a v i o u r o f Ruddy b r o o d p e r i o d . W i l d f o w l 28: 126-128.  and Maccoa  Ducks  during  85  Skutch, A.F. 1962. 115-152.  The  constancy  of  incubation. Wilson  Bull.  74:  S w a n s o n , G.A. 1978. A s i m p l e l i g h t w e i g h t c o r e s a m p l e r f o r q u a n t i f y i n g w a t e r f o w l f o o d s . J . W i l d l . M a n a g e . 42: 426428.  S w a n s o n , G.A. and J.C. B a r t o n e k . 1970. B i a s a s s o c i a t e d w i t h a n a l y s i s i n g i z z a r d s of Blue-winged T e a l . J . W i l d l . M a n a g e . 34: 7 3 9 - 7 4 6 .  food  S w a n s o n , G.A., G.L. K r a p u , J . C . B a r t o n e k , J.R. S e r i e a n d D.H. Johnson 1974. A d v a n t a g e s i n m a t h e m a t i c a l l y w e i g h t i n g w a t e r f o w l f o o d h a b i t s d a t a . J . W i l d l . M a n a g e . 38: 3 0 2 - 3 0 7 .  T a l e n t , L.G., Mallard 74-78.  Tome, M. in  R . L . J a r v i s , a n d G.L. Krapu. 1983. S u r v i v a l o f b r o o d s i n s o u t h - c e n t r a l N o r t h D a k o t a . C o n d o r 85:  1981. R e p r o d u c t i v e b i o e n e r g e t i c s o f f e m a l e Ruddy D u c k s M a n i t o b a . M.S. t h e s i s . U n i v . M a i n e ( O r o n o ) . 67 p p .  . 1984. C h a n g e s i n n u t r i e n t r e s e r v e s a n d o r g a n s i z e o f f e m a l e R u d d y D u c k s b r e e d i n g i n M a n i t o b a . Auk 101: 8 3 0 - 8 3 7 .  W e l l e r , M.W. 1959. P a r a s i t i c egg a m e r i c a n a ) and o t h e r N o r t h 29: 333-365.  Zar,  l a y i n g i n the Redhead (Aythya A m e r i c a n A n a t i d a e . E c o l . Monog.  J.H. 1984. S e c o n d e d . B i o s t a t i s t i c a l A n a l y s i s . H a l l , E n g l e w o o d C l i f f s , New J e r s e y . 718 pp.  Prentice-  86  APPENDIX Description  This  study  Chilcotin 31.5  Creek,  study  site  Canadian range  30  was  located  shallow map,  study  used  which  by  site. Canadian  on  water  the  waterfowl 50-1500 shallow  forest beetle. Munro  (1945),  the  region  with  ponds  numbered Service  has  been  the  degrees  North) Much area  near of  the  of  the  i s dominated  conifer  Water  these  ponds. at  3 m  or  by  groves  less)  Scaup,  American  and  Scudder  and  Mann  depth  system  by  CWS  ponds  commonly  this  ranges tended  were use  Cinnamon cattle,  and  are  Scudder  of  to  be  ponds  for  Teal.  infestations  from  by  Teal,  and  and  ringed  the  Green-winged  area  this  characteristics  Ponds  for grazing  in  biologists  conductivity  and  (1968),  the  working  Redhead,  of  through  biologists  logged after  descriptions  roads  to  most  which  Widgeon,  extensively being  and  major  according  degrees).  Waterfowl  Lesser  are  25  and  conducted  of  Further  minutes  training  Chilcotin  fauna,  i s used  areas  58  in  122  W i l l i a m s Lake.  chemistry, flora,  include  grassland  are  Wildlife.  scirpus.  Teal,  shows  research  ( d e p t h was  breeding  of  Prairie  (Longitute:  a military  The  7,  (micromhos/cm  emergent  winged  use  degrees  is interspersed  Ponds  Extensive  Beecher's  ponds.  Figure  area.  Site  Columbia  51  within  Forces.  grassland  A  British  Latitute:  Study  at  m i l e s southwest  Armed  numerous  the  West,  of  conducted  p a r k l a n d s of  minutes  Riske  was  ONE  BlueRange  coniferous pine  provided (1969).  bark by  88  APPENDIX Ambient  Temperature  Most stored  north  energy  Korshken, energy  1976c),  sufficient appears  more when  to hatch  which must  t o them on  i t i s warm Ruddy  incubation  much  1962)  when  and sunny  Ducks  may  because  feed  from  they  f o r short  (Siegfried  temperature  and  thus,  how  spend much  and r a i n y  and C o r n w e l l , feed  later  when  o f fthe time  mallards tended  to  et  Ambient ducks  able  (Tome,  temperatures  female  i t i s cold  their  nest  time  Female  breed  intake  intensively  on  1977;  85% of  the nest  to maintain  (Caldwell be  fuel  dietary  successfully.  how  nest  by  heavily  to  than  is  spend  they  do  1975).  Thus,  extensively  during  ambient  temperatures  higher. In  this  appendix,  temperature  of  the effect  Ruddy  of  dependence  of the female  also that  ambient  Ducks  influence  to  they  rely  (Ankney,  females  absent  for feeding.  the  Ruddy  be a b l e  eggs  influence  time  female  are  during  species  incubation  incubation  (Low, 1941; S k u t c h ,  available  fuel  frequently  yet they  to  to  for  are  of time  waterfowl  In c o n t r a s t ,  requirements  periods  nest  reserves  They  Breeding  temperate  1977).  1984).  al.,  and L a t e  TWO  discussed. i n summer,  that  i s  temperature  o f ambient  temperature  considered.  The  on t h e t i m i n g  on e n d o g e n o u s  energy  temperature  in spring  and nest  temperature  o f Ruddy  Coots.  potential  of b r e e d i n g and  for incubation are  Ambient  of American  on n e s t  i s Ducks  compared  to  i s compared  89  Comparison  In  of  1984,  difference Coots  Ambient  an  permanent  and nest  vegetation  of  measured  range  1983.  At  was  fixed  of  not  two  each  19  and  was  minimum  Student's in  s p r i n g - were  in  summer.  C.  in  those  second with  and  Spring  the  and  in Figure  to  time  of  number  t o be  by  fell  10  of  within  the  sites  in  nest  thermometer  at  bowl.  a  At  distance each  (1949) 34  throughout  from  May  Average  27  of  peak  Coot  to August  2  and  was  Ruddy  Duck  were  incubation. compared  r e c o r d s below  freezing to  34  by  those  degrees  the  maximum  temperature  Six  average  maximum minimum  spring was  the  to  incubation  C.)  and  summer  to  time  r e c o r d s above  found  degrees  minimum  (p<.001).  of  site,  chi-squared contingency test  average  maximum  emergent  chi-squared contingency test  than  spring  the  extended  peak  number  higher  the  Fifteen  marsh,  the  when  nest.  Duck  temperatures  significantly summer  first  the  spring  recorded daily  the  (Huggins  8.  were  July  total  summer  nest  from  by  i n the  selected  encompass  total  describe  within  i n the  the  The  compared  birds  to  maximum-minimum  was  The  were  of  from  maximum  compared  i n summer.  temperature  cm  Summer  Ducks  f o r Ruddy  anchored  chosen  Also,  spring  compared  pole  t-test.  sites  Springfield  periods.  to coincide  Average  The  temperatures  day  The  a  Ruddy  established  measurement  40  minimum  conducted  when  ponds.  than  incubation. chosen  were  wooden  twenty-four  June  sites  site,  and  ( a i r ) temperatures  summer  each  in Spring  was  the  of  to a  and  ambient  eight  more  maximum  experiment  between  nest  Temperature  temperatures temperature  minimum  (p<.00l)  significantly percent  of  higher  the  are was and than  recorded  90  LATE  MINIMUM  FIGURE 8 : Comparison temperatures e a r l y  of average  MAXIMUM  maximum  and  minimum  ambient  (when most Coots nest) and l a t e i n the season  (when most Ruddy Ducks nest)  91  minimum  temperature  whereas  t h e r e were  freezing  in  records  no minimum  the  summer.  in  spring  were  temperature This  below  records  difference  was  freezing,  at  or  below  s i g n i f i c a n t tit-  t e s t , p<.001 .  Ruddy  Duck  and American  Temperatures were  taken  being  monitored. t h e May  Ruddy  Duck  period. mercury  after  on  Coot  Average degrees  less  significantly  i n the  incubation  p e r i o d s when  ambient  temperatures  t o be  could  Coot  19 p e r i o d , taken  were  by  the July placing  Often  encouraged  to leave  be  taken. Average  n e s t s were nest that  different  at  so  Student's  Ducks  p<.0005.  were  measured  was  the and were that  bulb  of  recording found  2 a  the  sitting  temperature were  o f Ruddy  never  Duck  and  t-test.  24.1  (30.7  of  10 t o A u g u s t  females  temperature  temperature  o f Ruddy  Coots  Ruddy  c o m p a r e d by  were  stage  whereas the temperatures  during  taken,  nests  minutes.  the nest.  than  of  i n the c e n t e r of the n e s t  five  Coot  Temperatures  t o be  were  thermometer  discovered  known  t o June  Temperatures  measurements  Nest  Temperatures  27  n e s t s and had  American  the  nests  temperature on  of n e s t s  during  during  Coot  degrees  degrees  C , C.)  6.6 and  92  Conclusions  Eggs  warmed  by  incubation  temperatures  of  spring  temperatures  at  or  the  spring  and  temperatures  average than does  Ruddy  not  daily  when  the  the  Duck  mean  temperatures  than  incubated  and  the  if  were  Coots the  were  (Batt  and  when  Mallard  contrast, the  left  due  same  were  allowed since  rarely  on  the  exposure  (1972)  eggs  showed  were  both  of  eggs  that  exposed  on  Ruddy  Ducks  higher  to and  to cold,  would  females  ducks  success might  in  occurred  temperatures.) unlikely  i t i s warmer  or  result.  mortality  be  lower  incubation  hatching  freezing  because  cool males  the  difference  during  some  to  a  nest  that  i f incubating  reduced  d i s t u r b a n c e i n summer  effect  to  unattended  nest,  of  showed  Such  in  incubation  significantly  temperature.  Ducks,  was  was  u n d i s t u r b e d ; however,  to  Cornwell  such  nests  Ruddy  disturbed  spring,  nest  minimum  Measurements nest  cold  frequently  approaching  o f f the  temperature  Coot  nest  was  i n the  Daily  o c c u r r e d more  frequently.  Coots  rapidly  summer.  temperatures  female  nest  that  in  freezing  maximum less  average  they  below  occur  temperature  than  c o o l e d more  In  to  have  when  they  nest. If of  time  a  female  to  search  temperatures females  do  species  are  leave (Tome,  leaves the for food, warmer the  unattended  breeding could  nest  1981)  nest  more  later  reduce  out  i s convincing evidence  that  in  the  egg  often  perhaps  for extended  season  mortality.  than of  periods  other  necessity  when Ruddy  waterfowl to  avoid  starvation. There  Ruddy  Ducks,  unlike  other  93  waterfowl,  undergo  (Joyner, duck, o f often  of  1978). their  the  females nests  and  were  Cold  nests  cool  to  However,  to  When are  maintaining difficult  the  a and  early  spring  period  predation  appears  are  would  mean  warmer,  they  most 1954).  period  vulnerable Since  may than to  Ruddy  down,  the  be  a  eggs  clutch i f Ruddy  sit  on  eggs  their  exposure  to  to  early breeding  species.  less  warmed  are  leave  of  lower, more  the  nest  incubation  feeding  bouts,  but  Since  longer  nest  incubation  predation.  incubate  while  be  becomes  fuel  not  female.  temperature  females  survival  spend  must  probably  higher  predators  short  would  the  temperatures  spring,  egg  but  lengthened.  the  females  of  eggs  short  in  likely  the  possible  be  result  frequent  days  when  frequent  in  have  Ducks  a  (Tome,1981).  laying  absence of  slow  likely  Ruddy  i t  to  are  temperature  taking  prolonged  because  nest  ambient  may  heavier  had  for  Ruddy  prohibitive,  a f f e c t e d by  If  would  Finally,  incubation  be  i t might  by  laid  necessarily  (number  incubation  Thus,  c l u t c h of  be  they  the  in  1954).  incubation  periods  may  large, eggs  migrating,  not  from  development  cool.  which  insulated with  occurs)  high  female  migration  mortality.  do  period  spring  very  A  because  egg  lay  might  temperature  (Nice,  also  to  1968).  i t  absences  incubation  eggs  prior  molting,  feed  avoid  well  hatching  in  of  incubating  ambient  eggs  the  temperatures  and  and  (Lack,  cost  to  molt  females  than  unable  mortality.  the  more  constantly  before  size  combined  eggs,  wing  Ruddy  body  weighs  Thus,  a  sitting time  when  temperatures  rates  through  Females on  the  sitting  on  may  the be  nest  (Lack,  the  nest,  94  there  will  on the  nest.  be  fewer o p p o r t u n i t i e s for predators  to a t t a c k them  95  APPENDIX Nest  Predation  Early  results  experiment have  A  located  flagging banded  of Flagged  tape. with  Picozzi  (1975).)  in  marsh  the  investigate in  when  is  A twenty A  presence  I  might  have  dummy four  nest days  beginning dummy  dummy  the  experiment.  location,  unflagged in  dummy  (referred at  sites  birds  nests)  by f l a g g i n g  nests  which  flying  been on  (experiment  were  the  by  have  me  or  observed  and  come  o f dummy both  greater nest  to  nests  of  these  i n the spring predation,  during  was  nest  of  building  If flagging  f r e q u e n t l y than A).  a f f o r d e d good  after  tape  as  predators  cover  a  would  flagged nests  dummy  as  in  were n o t clue  find  to  these  (constructed  eight  dummy  nests  were  built  nests)  to conceal  unflagged-concealed  unflagged-  nests  provided  for  experiment  monitored  of these  In a d d i t i o n ,  overhead  conducted  t o here  constructed and  The p o s i t i o n s  An  B)  (referred  as unflagged-concealed  above.  near  demonstrated  nests  May 3 1 , 1 9 8 4 , a week  experiment  t o here  might  i n t h e marsh  i t was p r e d i c t e d t h a t  nest  might  predation  The e f f e c t  nests  tape.  less  predators areas  was  by one  have  nest  appendix.  unconcealed  nest  might  experiment  Eight  first  caused  a n d my p r e s e n c e  i n this  eggs  dummy  to associate colour  constructing  been  dense.  that  crows  Heavy  of  marsh  predators  I had l e f t .  was l e s s  began.  marked  was  of of  Alternately,  effect  discussed  One) s u g g e s t e d  ability  the  Nests  replicate  (The  when  tape  spring  by i n v e s t i g a t i n g  and their  cover  flagging  the  Dummy  nests  after  the spring  factors,  and Concealed  (see Chapter dummy  canes  of  THREE  nest  eggs would  from be  96  difficult build  for a predator  the  located  nest.  on e a c h  nests  of eight  ponds.  nests  constructed  Results  unless  One c o n c e a l e d  unflagged-concealed dummy  to find  are  contained  were  unflagged-unconcealed  and  five  i n experiment  A  in  eggs  Figure  9.  to  flagged-unconcealed  constructed no  between  nests.  T h e number  were  i n number  unflagged-unconcealed  significantly that  difference  lower  preyed  of concealed than  upon  like  nests  respects.  i s  nests  that  t h e number  (chi-squared  of  were  were  preyed  unconcealed  contingency  nests  There  and flagged-unconcealed that  of  compared  ( i e .  A).  of nests  nests  the  Predation  i n the spring p o r t i o n of experiment  significant  upon  a n d were  i n a l l other  and u n f l a g g e d - c o n c e a l e d  of  me  nest  unflagged-unconcealed predation  h a d seen  and one u n c o n c e a l e d Both  presented  the predator  was  preyed dummy  u p o n was  nests  test,  that  p<.00l).  Conclusions  Results tape  placed  of  experiment  at a distance  nest  construction  rates  observed  searching unflagged Similarly, areas  near  predicted would by  the  be  the nest  near  they  would  found  observed  nest  predation  similar.  Neither  experiments.  If  flagging  predators  where  that  n o r my-  neither  predators  tape, be  solely  building  of concealed of these  nest  found  during  predation nests  predicted that  destroyed  nests me  I  flagging  behavior  responsible f o rthe high  flagged nests  i f  that  from  suggested  i n the spring.  areas than  was  B  by by  by  fewer  predators.  investigating  dummy  nests,  and unconcealed  p r e d i c t i o n s was  I  nests  confirmed  97  O O -i  n =30  nr 8  o  CO  a  ID  n= 8  a *9  o  (VI  o -J-  FLA66E0 UNCONCEALED  FIGURE  9  concealment  :  Comparison  UNFLAGGED UNCONCEALEO  of  on t h e p r o p o r t i o n s  the  UNFLA66E0 CONCEALEO  effect  of  o f dummy n e s t  flagging predation  and nest  98  APPENDIX Green  Vegetation  Siegfried Ducks  was  He  early  (1976a)  suggested in  building. was  the  this  Data  that  on  that  region  eggs  seasonal  Ruddy  of  availability were  required  nest  British  nesting  of  green  green  green  in  the  ideas on  are  nest  Columbia  Ruddy  nesting ready for  in  vegetation  nests  of  other  presented  Ruddy  1983  vegetation  to nest  composition,  p a r a s i t i s m of  in green  in  vegetation  until  parasitically  of  Ducks  physiologically  nesting  information  variation  of  timing  Siegfried's  timing of  the  females but  refute  the  that  delayed  laid  Initiation  the  I discuss  and  Chilcotin  •Data  found  they  or  appendix.  initiation, the  Clutch  spring,  Thus,  available  birds.  the  c o r r e l a t e d with  cover. lay  and  FOUR  nest  Ducks  and  height  in  in  1984.  are  also  presented.  Nest  Composition  All study  Ruddy area  constructed seven dead There to  Duck were  of  green  percent  of  vegetation was  occur  no  more  nests  I discovered  examined or  dead  these  38.5%  tendency  for  determine  vegetation.  nests  (1983:  frequently  to  i n the  were  n=13 nests  either  Beecher's whether  On  1984:  constructed  e a r l y or  late  they  average,  constructed nests;  Prairie were forty-  completely 50.0%  of  dead  in  the  from n=30).  vegetation season.  99  Laying  Chronology  The  date  initiation) date,  the  total one  was  in  the  In  1983,  of  day).  the  the  initiated  period  eggs  initiated  nest  initiation  two  dates.  Except  are  for  sample  and  July  June  quite the  size in  most  early in  In  while  evenly  may  have  1983,  large  hatching  1980) laid  a  the  rate  versus  in  was  1984,  the  latest  10.  May  clutches  of  week  Figure  Ruddy  distributed  two  and  at  nests 1984  the  clutch-, the  the  initiation  5.  17  of  and  (clutch  22 were  earliest  was  July  between  24  these  (initiated  in  years  similar.  was  misrepresented samples  in  May,  the  1984  true  eliminated  possibility.  Utah  and  June.  ducklings they  on  clutch  18  and  was  clutches  populations  late  (eggs  for  Duck  chronology  Considerable  in  clutch  nest  from  Bellrose,  1983  18  of  days-  given  are  each  subtracting  season  June  small  in  number  between  Although  laid  comparing  July  laying  by  the  was  1983),  was  Histograms  and  this  in  e a r l i e s t Ruddy  was  egg  (24  latest  nest  timing  first  established  breeding  Ruddy  the  incubation  number  per  and  that  are  in in  of  variation  Ruddy  found  Ducks.  that  In  laying  contrast,  England British  in  were  laying  chronology  Joyner  (1975)  began Hudson  usually  Columbia.  in  late (1976)  raised  exists  studied April  and  reported  in July  and  between  Ruddy  Ducks  ceased that  in  Ruddy  August,  as  100  09 -|  m  o  01 10 -  a UJ  CO rul Ul  z  li.  o  LEGEND  or tu co  WEEK  1- MAY 20-26  WEEK  2- MAY 27-JUNE 2  WEEK  3- JUNE 3-9  WEEK  4- JUNE 10-16  WEEK  5- JUNE 17-23  WEEK  6- JUNE 24-30  WEEK  7- JULY 1-7  WEEK  8- JULY 8-14  WEEK  9- JULY 15-21  X  Z  o  J-  1  1 2 3 4 5 6 7 8 9  10  WEEK IN THE NESTING SEASON  ro at  WEEK 10- JULY 22-28  a ui  u  r-  0)  (E Ul ffl X  1 2 3 4 5 6 7 8 9  10  WEEK IN THE NESTING SEASON  FIGURE  10 : C o m p a r i s o n  and 1984.  o f Ruddy  Duck  clutch  initiation  i n 1983  101  Seasonal  Patterns  In by  1983,  at  gathered June  30,  studied and  of  five  times  seven  four  While  surface  by  of  for  females  to  80  began  a  In  13,  for  May  height the  single  years,  when  green and  shoots these  green  assessed  green-  condition.  Because  considerably  lower  clutch  initiation  likely  that  some  green  in  1984  began other  height  required  in  bring  the  factor  20  height and  same w e e k determines  40  when  the  and water  probably both  not  years,  height  averaged  likely  does  weeks  must  before  the  not have  laying  appropriate  into prior  in both  30  were  1983  above  In  cm  to  is plotted  Females  for  was  17.  of  were  height  females  vegetation (between  summer  30,  pond  vegetation  several  May  Data  July  vegetation  initiated.  were  increased  mid-June.  are  which  was  shoots  clutches  changes  same  emerged  when  physiological  the  13,  15,  determine  is  May  June  vegetation  time  Data  31, of  (scirpus)  pond.  station.  green  since  bulrush  each  however,  vegetation  established  at  building until laying  was  season:  cm;  occurred,  five  1984,  spring  vegetation  i n both  nest  of  breeding  measured  average  green  the  vegetation  water  25.  : May  date  green  stations monitored  were  mid-May  enough  Ruddy  number  calendar  1984.  tall  July  11,  of  above  during  times  Growth  s t a t i o n s on  and  shoots  Figure  against  eleven  12,  the  height  height  each  but  In  the  July  collected  70  average  measuring  shoots  in Vegetation  reproductive to  laying  lower), years,  Ruddy  was  while  i t seems  Ducks  breed.  102  10  • CV  X  So S-  X  z o M rn ¥— .  •  ?°  X  X  UJ CO UJ  > ID  Z  UJ UJ  O  X  cc CO  <  ^  X  o  •  2-* MAY 1  FIGURE  11  vegetation  • 1  I  j  JUNE 1  JULY 1  AUG 1  Comparison height  i n 1983  of  seasonal  (X) and  1984  changes  i n average green  (squares).  1 03  Nest  Parasitism  Nest Ruddy  Duck  monitor (see  parasitism laying  nest  chapter  parasitic in  dummy  nests  and  the  early  nesting  and ambient  the latter.  no Ruddy  that  to  i n 1984  eggs some  parasitic  simultaneously, A similar  up  of  d i dnot stimulate  In c o n t r a s t ,  suggesting  occurred  set  temperatures  since  nests.  t o the onset  nests,  Two), a p p a r e n t l y  dummy  parasitized  preceding  Joyner  rates  prior  Dummy  i n the season,  spring  were  detected  year.  one and Appendix  normal  former  not  in either  predation  laying  found  was  rather  result  were summer  nesting than t h e  was r e p o r t e d  by  (1983).  Conclusions  Because with  dead  delays shows  that  cm  available appears  green  females for  t o be most  breed  1 5 ) , many  water  (1974) began  nest  seems  Ducks  nests  laying  Ducks  building. after  do n o t u s e g r e e n female  nested  more  i n mid t o l a t e  also  reported  green  vegetation  Furthermore, green  study  vegetation i s  had emerged  before  vegetation This  a n d one Ruddy  (1975)  eggs  constructed  green  green  initiated  and Joyner  prevalent  when  i n t h e marsh  (clutch  that  were  unlikely.  Ruddy  the nest  vegetation  the  Misterek  Ruddy  species  Ruddy  June  Duck  the suggestion  f o rc o n s t r u c t i n g  above  1983). some  most  (after  most  only,  in this  while  vegetation before  50% o f a l l Ruddy  vegetation  breeding  abundant  20  nearly  than May that was  nest' p a r a s i t i s m  vegetation  i s  abundant  1 04  (late  June  material lay  and  early  July)  and  thus, the lack  i n the season cannot  parasitically  rather  explain  than n e s t i n g  of s u i t a b l e  nesting  why  females  normally.  Ruddy  

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