NEAFWA 2018

AUTHORS: Michael E. Akresh, Department of Environmental Conservation, University of Massachusetts Amherst; David I. King, U.S. Forest Service Northern Research Station; Peter P. Marra, Migratory Bird Center, Smithsonian Conservation Biology Institute

ABSTRACT. Recent findings that winter habitat quality can ‘carry-over’ to influence migratory birds on their breeding grounds poses a conundrum for managers in the US, who can only manipulate breeding habitat quality. We studied prairie warblers (Setophaga discolor) to assess winter habitat carry-over effects in a threatened migratory shrubland bird, and also examined whether carry-over effects can work in the opposite direction, testing if breeding habitat quality influences birds on their wintering grounds. For prairie warblers in the wintering grounds, moisture is highly correlated with habitat quality, and moisture/habitat quality also correlates with carbon stable isotope samples from birds. Using stable isotopes from birds’ claws and red blood cells collected on the breeding grounds, we first assessed if winter habitat quality in the Caribbean carried over to influence birds’ phenology and reproductive success in Massachusetts, USA. In two of three years, adult males wintering in drier habitat arrived later on the breeding grounds, but winter habitat did not influence reproductive performance for males or females. Using the North Atlantic Oscillation index to indicate winter rainfall and carbon isotopes to indicate winter habitat quality, we also examined carry-over effects initiated during the breeding season. Juvenile birds that hatched earlier acquired wetter winter habitat during drier winters, and during all winters for male birds. Winter habitat acquired as a juvenile was used throughout the bird’s life. Therefore, an individual’s hatching date, which can be correlated with breeding ground habitat quality, can influence a bird’s lifetime winter habitat quality. Based on our full life cycle analysis, we found that the creation and maintenance of suitable early-successional breeding habitat is very important in sustaining prairie warbler populations. We recommend researchers and managers consider the full annual cycles of wildlife to provide the best management tools and conservation actions for declining and threatened species.