Using stable hydrogen and oxygen isotope measurements of feathers to infer geographical origins of migrating European birds

Successful application of stable-hydrogen isotope measurements (delta(f)) of feathers to track origins of migratory birds and other wildlife requires a fundamental understanding of the correlation between delta(f) and deuterium patterns in rainfall (delta(p)) over continental scales. A strong correlation between delta(p) and delta(f) has been confirmed for birds and insects in North America, but not yet for other continents. Here, we compare delta(f) data from resident European birds to new delta(p) basemaps for Europe. Three maps, representing growing-season and mean annual delta(p) estimates from an elevation-explicit, detrended interpolation model and growing-season delta(p) estimates from simple Kriging, all indicate that strong isotope gradients occur across Europe with a general depletion occurring in a northeast direction. The feather data, representing 141 individuals of 25 avian species from 38 sites, ranged from -131 to -38%. Regression analysis showed that strong correlations existed between both mean annual and growing-season delta(p) estimated by detrended interpolation and delta(f) of non-aquatic and non-corvid birds (r(2)=0.66 and 0.65, respectively). We also examined mean annual and growing-season delta(18)O(p) vs. delta(18)O(f) for our samples. Both oxygen regressions were similar (r(2)=0.56 and 0.57, respectively) but poorer than for deuterium. Our study reveals that deltaD measurements of feathers from migratory birds in Europe may be used to track their origin and movements, and so provide a powerful investigative tool for avian migration research in Europe.