ARE LATE-SPRING BOREAL LESSER SCAUP (AYTHYA AFFINIS) IN POOR BODY CONDITION?

DeVink, Jean-Michel; Clark, Robert G.; Slattery, Stuart M.; Trauger, David L.

doi:10.1525/auk.2008.06171

Cited by 17 publications

(20 citation statements)

References 23 publications

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“…A relatively inflexible strategy such as this is corroborated by observed patterns in scaup. Breeding in scaup is initiated during a narrow window of time across a broad range of latitude and elevation (DeVink et al 2008, Gurney et al 2011), a possible product of strong heritability of nest initiation date (Findlay and Cooke 1982). If timing of breeding is the sum of heritable nest initiation date and nonheritable influences of body condition and environmental factors (sensu Price et al 1988), then the latter would appear to have the weakest influence on timing of breeding, and thus clutch size, in scaup.…”

Section: Discussionmentioning

confidence: 99%

Body condition dynamics and the cost‐of‐delay hypothesis in a temperate‐breeding duck

Warren

Cutting

Koons

2013

Journal of Avian Biology

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Pre-breeding body condition is an important determinant of reproductive success in birds, largely through its influence on timing of breeding. Declines in clutch size and recruitment probability within breeding seasons indicate a tradeoff may exist between the number of young (clutch size) and quality of young (recruitment probability). We explored local drivers of pre-breeding body condition and tested predictions of the cost-of-delay hypothesis in female lesser scaup Aythya affinis. Yearling females arrived on the study site in lower body condition than older females, but both age classes had similar rates of body condition gain on the breeding grounds prior to nesting. Rates of body condition gain were positively influenced by water temperature, a proxy for wetland phenology. The effect of water level was asymptotic and interacted with water temperature, with greater rates of gain in body condition occurring in years with low water levels. Our results supported the predicted response of clutch size to the rate of pre-breeding body condition gain. After accounting for lay date, clutch size was positively related to the rate of body condition gain (b  0.08  0.039). We did not find support for a predicted interaction between rate of body condition gain and intra-seasonal decline in clutch size (b  0.01  0.01). Our results indicate that local conditions during pre-breeding influence body condition dynamics in female lesser scaup, which subsequently affects clutch size.

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Section: Discussionmentioning

confidence: 99%

Body condition dynamics and the cost‐of‐delay hypothesis in a temperate‐breeding duck

Warren

Cutting

Koons

2013

Journal of Avian Biology

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“…Decoy-trapped females were lighter than shot females after accounting for temporal effects and ingesta mass. The difference was more pronounced in 2004, when females generally were lighter than in 2003, possibly due to a late spring thaw (Environment Canada 2004*) which may have reduced food availability (Devink et al 2008). We suspect the mass difference between methods was due to a greater proportion of yearlings or poorer quality females in the decoy-trapped sample, but could not test this hypothesis.…”

Section: Body Condition and Age Bias Associated With Decoy Trapsmentioning

confidence: 95%

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

et al. 2008

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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.

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“…Similarly, on the breeding grounds, lipid reserves of females recently arrived in the southern Manitoba parkland in 2000 and 2001 were much lower than 1977-1980 values (Anteau and Afton 2004). For boreal breeding scaup, historical nutrient reserve data are sparse (body mass only; Trauger 1971) but lipid reserves of boreal females measured during [2003][2004] in northern Alberta and the Northwest Territories were much lower than historical values reported for females in northwestern Minnesota in 1986-1988and southwestern Manitoba in 1977-1980(Anteau and Afton 2004, 2009a; but see DeVink et al 2008c). Furthermore, recent studies have reported that some reproductive parameters, such as nest success, female survival, duckling and brood survival, and breeding probability, were low in boreal and parkland breeding sites, at rates that would be consistent with the SCH (Fournier and Hines 2001;Brook 2002;Koons and Rotella 2003;Corcoran et al 2007;Martin et al 2009).…”

Section: Introductionmentioning

confidence: 87%

Reproductive Rates in Lesser Scaup (Aythya affinis) in Southwestern Manitoba: Another Look at the Data

Hammell¹

2016

Can Field Nat

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Surveys indicate that Lesser Scaup (Aythya affinis) populations declined during the early 1980s and have since remained below conservation goals. Reasons suggested for the decline include chemical contamination, climate change, and reduced food resources. According to the latter theory, reproductive success of Lesser Scaup has declined because females now arrive on the breeding grounds with fewer nutrient reserves than in the past and this diminished body condition is the result of reduced food resources available at wintering and/or migration areas. To determine whether reproductive success has declined over time, I examined selected Lesser Scaup reproductive rates from 2008 to 2014 in southwestern Manitoba and compared them with those recorded before the continental population decline. Estimated productivity (age class IIa broods/pair), hatching date, Ia and IIa brood size, duckling survival rate (first sighting to age class IIa), and proportion of age class IIa broods with females in attendance were unchanged from values recorded in 1970–1972. Thus, if females are arriving on southern breeding areas with reduced body reserves, they may be recovering these losses before nesting, enabling them to attain reproductive rates similar to those in the past. In addition, these results are consistent with the hypothesis that reduced food resources at non-breeding areas could affect recruitment of southern prairie-parkland breeders to a lesser extent than northern breeders because of the longer time between arrival and egg-laying in the south.

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ARE LATE-SPRING BOREAL LESSER SCAUP (AYTHYA AFFINIS) IN POOR BODY CONDITION?

Cited by 17 publications

References 23 publications

Body condition dynamics and the cost‐of‐delay hypothesis in a temperate‐breeding duck

Body condition dynamics and the cost‐of‐delay hypothesis in a temperate‐breeding duck

Eye Colour, Aging, and Decoy Trap Bias in Lesser Scaup, <em>Aythya affinis</em>

Reproductive Rates in Lesser Scaup (<i>Aythya affinis</i>) in Southwestern Manitoba: Another Look at the Data

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