OVERWINTER SURVIVAL OF NEOTROPICAL MIGRATORY BIRDS IN EARLY-SUCCESSIONAL AND MATURE TROPICAL FORESTS

Many Neotropical migratory species inhabit both mature and early-succe ssional forests on their wintering grounds, yet comparisons of surviva l rates between habitats are lacking Consequently, the factors affecti ng habitat suitability for Neotropical migrants and the potential effe cts of tropical deforestation on migrants are not well understood. We estimated overwinter survival and capture probabilities of Wood Thrush (Hylochichla mustelina), Ovenbird (Seiurus aurocapillus), Hooded Warb ler (Wilsonia citrina), and Kentucky Warbler (Oporornis formosus) inha biting two common tropical habitat types, mature and early-successiona l forest. Our results suggest that large differences (for example, rat io of survival rates (gamma) less than or equal to 0.85) in overwinter survival between these habitats do not exist for any of these species . Age ratios did not differ between habitats, but males were more comm on in forest habitats and females more common in successional habitats for Hooded Warblers and Kentucky Warblers. Future research on overwin ter survival should address the need for age- and sex-specific surviva l estimates before we can draw strong conclusions regarding winter hab itat suitability. Our estimates of overwinter survival extrapolated to annual survival rates that were generally lower than previous estimat es of annual survival of migratory birds. Capture probability differed between habitats for Kentucky Warblers, but our results provide stron g evidence against large differences in capture probability, between h abitats for Wood Thrush, Hooded Warblers, and Ovenbirds. We found no t emporal or amongsite differences in survival or capture probability fo r any of the four species. Additional research is needed to examine th e effects of winter habitat use on survival during migration and betwe en-winter survival.