Many migratory bird species, including the American Black Duck (Anas rubripes; hereafter black duck), face challenges to their survival during winter due to potentially limited resources and high energetic demands. These winter processes can be especially important for the population dynamics of migratory species. Despite stabilization of the overall black duck breeding population, historical declines continue for black ducks wintering in the Mississippi Flyway. It remains unclear if declining abundance in this region reflects high winter mortality. We radio-tagged 111 females in the Tennessee National Wildlife Refuge (TNWR), a major wintering area for mid-continent Mississippi Flyway black ducks, from December to February of 2010–2012 to estimate winter survival and investigate factors that may influence survival rates, including body mass, age, hunting period, and weather. Winter survival (0.83–0.85) was greater than or comparable with previous estimates for black duck populations in North America. Generally, birds with greater body mass had higher survival than birds of lesser body mass; a bird 100 g heavier than one of average body mass had 18% greater interval survival. We also found that body mass had a greater influence on survival during late (nonhunting) periods and a more severe winter, when resources potentially were limited. For example, a bird with a body mass 100 g above average had 9% greater interval survival than one of average body mass during the winter of 2010–2011, but in the subsequent milder winter, the heavier bird had similar survival to the bird of average body mass. Our results suggest that winter mortality is not a primary factor contributing to declining abundance of black ducks in the TNWR. If this reflects the general pattern in the Mississippi Flyway, declining regional abundance may be driven by movement patterns or cross-seasonal effects rather than winter mortality.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 118 • No. 1