Annual and seasonal survival of adult female Mottled Ducks in southern Florida, USA

Abstract

Continuing human population growth and urbanization in Florida may impact the survival of native birds, including the Florida Mottled Duck (Anas fulvigula fulvigula). Survival of adult females is an important vital rate that affects population growth rates, thus estimates of female survival as well as sources of variation affecting survival rates are needed for the development of a more informed conservation plan for Florida Mottled Ducks. In this study, we estimated annual and seasonal survival rates of radio-tagged adult female Mottled Ducks (n = 236) using urban and rural areas in southern Florida from 2008 to 2011. Additionally, we tested for differences in survival among ducks using different geographic areas during the breeding season and that were exposed to different hunting regimes during the hunting season. Identifying the geographic areas where higher rates of mortality occur may allow for more effective habitat and harvest management of the Florida subspecies of Mottled Duck. Annual survival was higher for ducks that used urban areas (74%) than for ducks that did not (47%). Daily survival rates were lowest during the breeding season. Females that used Everglades-type habitat during the breeding season had higher seasonal survival rates (78–85%) than those that did not (37–47%). We found evidence of density-dependent mortality during and after the hunting season. Differences in hunting season survival for ducks that used unhunted rural areas (88%) when compared with survival of ducks that used areas with open (87%) or quota hunting systems (85%) were not significant. Differences in survival among study years were negligible. Our results indicate that Florida Mottled Ducks survive at high rates in urbanized areas, but may benefit from increases in the quantity and quality of breeding habitats.