A forensic approach to understanding diet and habitat use from stable isotope analysis of (avian) claw material

1. The potential of using stable isotope signatures of avian claws in order to infer diet and habitat use was investigated. 2. Highly significant relationships observed between stable carbon and nitrogen isotope ratios ( δ 13 C, δ 15 N) in the claws and body feathers of resident birds were expected since it was predicted that they were synthesized in the same habitat and approximately the same time of year. 3. Likewise the non-significant relationships observed between δ 13 C and δ 15 N in the claws and tertial feathers of neotropical migrant birds were also predicted since the claws were synthesized in the wintering area and the tertials in the breeding area. 4. The growth rates measured in the claws of five species of palearctic passerines provide evidence that this tissue should integrate dietary and habitat information over a medium temporal scale (probably weeks to months). 5. It is suggested that claws may offer a unique combination of attributes to the isotope ecologist: they are non-invasively sampled; metabolically inert but grow continuously, and are therefore a more flexible tool than feathers. 6. It is also suggested that that the stable isotope signatures in the claws of mammals and reptiles may provide similar information.