ESTIMATING ORIGINS OF THREE SPECIES OF NEOTROPICAL MIGRANT SONGBIRDS AT A GULF COAST STOPOVER SITE: COMBINING STABLE ISOTOPE AND GIS TOOLS

Abstract

Abstract Measurement of stable-hydrogen isotopes (δD) in feathers of migrating birds can provide information on where feathers were grown in North America, at least to an approximate band of latitude. This approach has greatly increased our ability to investigate aspects of avian migration and stopover ecology, since origins of unmarked individuals at migration stopover sites can be estimated for the first time. However, few studies have explored the power of combining isotope measurements with geographic information system (GIS) methods. We measured δD values in feathers of hatching-year (HY) Swainson's Thrushes (Catharus ustulatus; n = 60), Wood Thrushes (Hylocichla mustelina; n = 113), and Gray Catbirds (Dumetella carolinensis; n = 158) at Ft. Morgan Peninsula, Alabama (30°10′N, 88°00′W), a migration stopover site along the Gulf coast. By applying an elevation-corrected hydrogen isotope basemap for birds in North America, we derived a GIS surface depicting expected feather δD values across the co...