Body condition and reproductive strategies of female lesser scaup in the boreal forest of Alaska

Abstract

In many waterfowl species, body condition of breeding females can contribute to reproductive success by influencing factors such as egg size, clutch size and ability to incubate eggs. In turn, changes in female condition at the population level could affect population growth rates. Large-scale declines in populations of Lesser Scaup (Aythya affinis) raised concerns that poor female body condition was contributing to declines by reducing reproductive output. However, little was known about changes in body condition over time and about the contribution that stored body reserves make to egg production, especially in boreal forest regions where most scaup breed. My objectives were: 1) examine temporal changes in body condition of pre-breeding female lesser scaup on the Yukon Flats National Wildlife Refuge, Alaska and the relationship between body condition and breeding status; 2) examine the role of body reserves (protein and lipid) in egg production using stable isotope techniques. I found no evidence for a decline in female body condition as compared to historic measures. However, females that had entered rapid follicle growth (the early stages of egg production) were significantly fatter than birds that were not currently producing eggs. In addition, I found that female lesser scaup use both body reserves and dietary nutrients for production of egg yolk.