scholarly journals Effects of Hatching Date and Egg Size on Growth, Recruitment, and Adult Size of Lesser Scaup

The Condor ◽  
2000 ◽  
Vol 102 (4) ◽  
pp. 930-935 ◽  
Author(s):  
Russell D. Dawson ◽  
Robert G. Clark
Keyword(s):  
Selective Advantage ◽  
Breeding Population ◽  
Adult Size ◽  
Hatching Date ◽  
Egg Volume ◽  
Brood Rearing ◽  
Aythya Affinis ◽  
Lesser Scaup ◽  
Local Breeding ◽  
Nutrient Reserves

AbstractEvidence suggests that birds breeding early in the season or laying larger eggs are at a selective advantage because quality and survival of their offspring are higher. We tested whether wild Lesser Scaup (Aythya affinis) hatching early in the season or from larger eggs had enhanced growth as ducklings and larger size or higher probability of recruiting to the local breeding population in years after hatching. After correcting for age at capture, body mass, head length, and culmen of ducklings were inversely related to hatching date, but were unrelated to egg volume. As adults, late-hatched birds had shorter wing lengths (second-year birds only) and tended to have smaller head lengths (all after-hatch year birds) than early hatching birds. We suggest that later-hatching birds are smaller due to increased competition for food during brood rearing. Recruitment probability increased as natal egg volume increased and decreased among birds with later natal hatching dates. We speculate these results are due to higher mortality of ducklings hatched from small eggs, and because early-hatched birds have more time to acquire nutrient reserves that would reduce vulnerability to costs of migration.

scholarly journals Eye Colour, Aging, and Decoy Trap Bias in Lesser Scaup, Aythya affinis

2008 ◽  
Vol 122 (1) ◽  
pp. 21 ◽  
Author(s):  
Marie Fast ◽  
Robert G. Clark ◽  
Rodney W. Brook ◽  
Peter L. F. Fast ◽  
Jean-Michel Devink ◽  
...  
Keyword(s):  
Breeding Population ◽  
Lower Body ◽  
Aythya Affinis ◽  
Lesser Scaup ◽  
Age Related ◽  
Eye Colour ◽  
Colour Changes ◽  
Local Breeding ◽  
Assignment Success ◽  
Trap Bias

Researchers routinely assume that samples of trapped or captured animals are representative of the overall population, though these assumptions are not always evaluated. We used decoy-trapped Lesser Scaup (Aythya affinis) to assess the reliability of classifying females as yearlings or adults from a distance, based on documented age-related eye-colour changes, and also to evaluate the presence of sex, condition and age biases in decoy trapping. We compared eye colour of trapped females to photographs of known-age females following a published procedure while females were (1) in traps (by using spotting scopes or binoculars) and (2) in-hand. Assuming in-hand age assessments were correct, we found that adults aged from a distance were frequently misclassified as yearlings, but yearlings were never misclassified as adults. Distance between observer and female, overall observation quality, and cloud cover did not influence age assignment success. A larger proportion of males was captured than observed during a survey of the local breeding population. We also found that decoy-trapped females had lower body mass and were more likely to be yearlings compared to pass- and jump-shot females from the same area. We conclude that female Lesser Scaup cannot be accurately aged from a distance using eye colour and concur with other researchers that possible sex, age and condition biases should be evaluated when using decoy traps.

scholarly journals Nutrient Reserves of Lesser Scaup (Aythya Affinis) During Spring Migration in the Mississippi Flyway: A Test of the Spring Condition Hypothesis

The Auk ◽  
2004 ◽  
Vol 121 (3) ◽  
pp. 917-929 ◽  
Author(s):  
Michael J. Anteau ◽  
Alan D. Afton
Keyword(s):  
Reproductive Success ◽  
Body Mass ◽  
Body Condition ◽  
Female Body ◽  
Population Decline ◽  
Spring Migration ◽  
Aythya Affinis ◽  
Lesser Scaup ◽  
Nutrient Reserves ◽  
Mineral Reserves

AbstractThe continental scaup population (Lesser [Aythya affinis] and Greater [A. marila] combined) has declined markedly since 1978. One hypothesis for the population decline states that reproductive success has decreased because female scaup are arriving on breeding areas in poorer body condition than they did historically (i.e. spring condition hypothesis). We tested one aspect of that hypothesis by comparing body mass and nutrient reserves (lipid, protein, and mineral) of Lesser Scaup at four locations (Louisiana, Illinois, Minnesota, and Manitoba) between the 1980s and 2000s. We found that mean body mass and lipid and mineral reserves of females were 80.0, 52.5, and 3.0 g higher, respectively, in the 2000s than in the 1980s in Louisiana; similarly, body mass and lipid and mineral reserves of males were 108.8, 72.5, and 2.5 g higher, respectively. In Illinois, mean body mass and lipid reserves of females were 88.6 and 56.5 g higher, respectively, in the 2000s than in the 1980s; similarly, body mass and lipid and mineral reserves of males were 80.6, 76.0, and 2.7 g higher, respectively. Mean body mass of females were 58.5 and 58.9 g lower in the 2000s than in the 1980s in Minnesota and Manitoba, respectively; mean body mass of males, similarly, were 40.7 g lower in Minnesota. Mean lipid reserves of females in the 2000s were 28.8 and 27.8 g lower than those in the 1980s in Minnesota and Manitoba, respectively. Mean mineral reserves of females in the 2000s were 3.2 g lower than those in the 1980s in Manitoba. Consequently, females arriving to breed in Manitoba in the 2000s had accumulated lipid reserves for 4.1 fewer eggs and mineral reserves for 0.8 fewer eggs than those arriving to breed there in the 1980s. Accordingly, our results are consistent with the spring condition hypothesis and suggest that female body condition has declined, as reflected by decreases in body mass, lipids, and mineral reserves that could cause reductions in reproductive success and ultimately a population decline.

Lesser Scaup (Aythya affinis)

2014 ◽  
Author(s):  
Michael J. Anteau ◽  
Jean-Michel DeVink ◽  
David N. Koons ◽  
Jane E. Austin ◽  
Christine M. Custer ◽  
...  
Keyword(s):  
Aythya Affinis ◽  
Lesser Scaup

Hepatic Element Concentrations of Lesser Scaup (Aythya affinis) During Spring Migration in the Upper Midwest

2010 ◽  
Vol 61 (1) ◽  
pp. 144-150 ◽  
Author(s):  
Angela E. Pillatzki ◽  
Regg D. Neiger ◽  
Steven R. Chipps ◽  
Kenneth F. Higgins ◽  
Nancy Thiex ◽  
...  
Keyword(s):  
Spring Migration ◽  
Upper Midwest ◽  
Aythya Affinis ◽  
Element Concentrations ◽  
Lesser Scaup

scholarly journals Survival of Female Lesser Scaup: Effects of Body Size, Age, and Reproductive Effort

The Condor ◽  
2003 ◽  
Vol 105 (2) ◽  
pp. 336-347 ◽  
Author(s):  
Jay J. Rotella ◽  
Robert G. Clark ◽  
Alan D. Afton
Keyword(s):  
Body Size ◽  
Natural Selection ◽  
Female Body ◽  
Reproductive Effort ◽  
Cost Of Reproduction ◽  
Aythya Affinis ◽  
Female Body Size ◽  
Lesser Scaup ◽  
Adult Females ◽  
Breeding Propensity

AbstractIn birds, larger females generally have greater breeding propensity, reproductive investment, and success than do smaller females. However, optimal female body size also depends on how natural selection acts during other parts of the life cycle. Larger female Lesser Scaup (Aythya affinis) produce larger eggs than do smaller females, and ducklings from larger eggs survive better than those hatching from smaller eggs. Accordingly, we examined patterns of apparent annual survival for female scaup and tested whether natural selection on female body size primarily was stabilizing, a frequent assumption in studies of sexually dimorphic species in which males are the larger sex, or was directional, counteracting reproductive advantages of large size. We estimated survival using mark-recapture methods for individually marked females from two study sites in Canada (Erickson, Manitoba; St. Denis, Saskatchewan). Structurally larger (adults) and heavier (ducklings) females had lower survival than did smaller individuals in Manitoba; no relationship was detected in adults from Saskatchewan. Survival of adult females declined with indices of increasing reproductive effort at both sites; consequently, the cost of reproduction could explain age-related patterns of breeding propensity in scaup. Furthermore, if larger females are more likely to breed than are smaller females, then cost of reproduction also may help explain why survival was lower for larger females. Overall, we found that advantages of large body size of female scaup during breeding or as young ducklings apparently were counteracted by natural selection favoring lightweight juveniles and structurally smaller adult females through higher annual survival.Sobrevivencia de Aythya affinis: Efectos del Tamaño Corporal, Edad y Esfuerzo ReproductivoResumen. En las aves, las hembras de mayor tamaño generalmente presentan una mayor predisposición a la reproducción, mayor inversión reproductiva y mayor éxito que las hembras de menor tamaño. Sin embargo, el tamaño óptimo de la hembra también depende de cómo la selección natural opera durante otras etapas del ciclo de vida. Hembras de Aythya affinis más grandes producen huevos de mayor tamaño que hembras más pequeñas, y los polluelos provenientes de huevos más grandes sobreviven mejor que aquellos que eclosionan de huevos más pequeños. Consiguientemente, examinamos los patrones de sobrevivencia anual aparente para hembras de A. affinis y probamos si la selección natural sobre el tamaño del cuerpo de las hembras era principalmente estabilizadora (una suposición frecuente en estudios de especies sexualmente dimórficas en que los machos son el sexo mayor), o era direccional, contrarrestando las ventajas reproductivas de un tamaño mayor. Estimamos la sobrevivencia de hembras utilizando métodos de marcaje y recaptura en dos sitios de estudio (Erickson, Manitoba; St. Denis, Saskatchewan). Hembras estructuralmente más grandes (adultas) y más pesadas (polluelos) tuvieron una menor sobrevivencia que individuos más pequeños en Manitoba; no se detectó una relación entre adultos de Saskatchewan. En ambos sitios la sobrevivencia de hembras adultas decreció con los índices de incremento de esfuerzo reproductivo; consecuentemente el costo reproductivo podría explicar los patrones de predisposición reproductiva relacionados a la edad en A. affinis. Además, si las hembras de mayor tamaño presentan mayor probabilidad de reproducirse que las hembras pequeñas, entonces el costo reproductivo también podría ayudar a explicar porqué la sobrevivencia fue menor para hembras más grandes. En general encontramos que en las hembras de A. affinis las ventajas de un tamaño corporal grande durante la cría o como juveniles fueron aparentemente contrarestadas por la selección natural que favorece juveniles de peso liviano y hembras adultas estructuralmente más pequeñas a través de una mayor sobrevivencia anual.

scholarly journals Nutrient Reserves and Clutch-Size Regulation of Northern Shovelers in Alaska

The Auk ◽  
2000 ◽  
Vol 117 (4) ◽  
pp. 971-979 ◽  
Author(s):  
Margaret C. MacCluskie ◽  
James S. Sedinger
Keyword(s):  
Clutch Size ◽  
Egg Production ◽  
Prairie Pothole Region ◽  
Prairie Pothole ◽  
High Productivity ◽  
Brood Rearing ◽  
Nutrient Reserve ◽  
Anas Clypeata ◽  
Nutrient Reserves ◽  
Nest Initiation

Abstract We determined patterns of nutrient-reserve use by female Northern Shovelers (Anas clypeata) nesting at Minto Flats, Alaska, and compared them with those of female shovelers nesting in the Prairie Pothole Region of Manitoba, Canada. Individual variation in somatic lipid was best explained by nest initiation date; females that initiated nests early had larger lipid reserves than females that delayed nest initiation. These results contrast with those from Manitoba, which showed that females used lipid reserves and stored protein during egg production. Incubating females from Alaska did not use protein or mineral reserves, but lipid reserves decreased significantly throughout incubation. Females in Alaska and Manitoba used lipid reserves similarly during incubation. We conclude that endogenous nutrient availability does not proximately limit clutch size during laying for this population of shovelers, possibly due to the high productivity of wetlands in interior Alaska and/or the long photoperiod that allow females to forage extensively. Successful completion of incubation or brood rearing may be an ultimate factor that controls clutch size for this population of shovelers.

An Outbreak of West Nile Virus Infection in Captive Lesser Scaup (Aythya affinis) Ducklings

2009 ◽  
Vol 53 (1) ◽  
pp. 129-134 ◽  
Author(s):  
Chelsea G. Himsworth ◽  
Kirsty E. B. Gurney ◽  
Aleksjia S. Neimanis ◽  
Gary A. Wobeser ◽  
Fredrick A. Leighton
Keyword(s):  
West Nile Virus ◽  
Virus Infection ◽  
West Nile Virus Infection ◽  
West Nile ◽  
Aythya Affinis ◽  
Lesser Scaup
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