Stable isotope evidence for Turkey Vulture reliance on food subsidies from the sea

Turkey Vulture (Cathartes aura) reliance on marine subsidies in coastal Baja California peninsula was quantitatively assessed by analyzing carbon and nitrogen stable isotope ratios in its feathers. Feathers were collected in two separate roosts in a small farm, a small fishing village and an uninhabited beach. We compared among them the isotopic niches of the four populations and also with those of Yellow-footed Seagull (Larus livens), Brown Pelican (Pelecanus occidentalis) and Orange-throated Whiptail lizard (Aspidoscelis hyperythra), used as reference for sympatric marine and terrestrial species. The importance of nutrients of marine origin varied among local close subpopulations, suggesting some spatial segregation. Dominant individuals would be established near predictable sources of food (human settlements), having a mixed terrestrial-marine diet influenced by local human activities (isotopic signature of feathers also indicated the role of human-fed cattle as vulture food). Subordinate individuals would be relegated to wandering along the beaches searching for washed up food, having a diet almost exclusively marine.