title: Use of stable isotopes to investigate keratin deposition in the claw tips of ducks.
abstract: Stable isotopes derived from the claws of birds could be used to determine the migratory origins of birds if the time periods represented in excised sections of claws were known. We investigated new keratin growth in the claws of adult female Lesser Scaup (Aythya affinis) by estimating the equilibration rates of stable isotopes (δ (13)C, δ (15)N, and δ (2)H) from the breeding grounds into 1 mm claw tips. We sampled birds on their breeding ground through time and found that it took approximately 3-3.5 months for isotope values in most claw tips to equilibrate to isotope values that reflected those present in the environment on their breeding grounds. Results from this study suggest that isotopes equilibrate slowly into claw tips of Lesser Scaup, suggesting isotopes could potentially be used to determine the wintering grounds of birds. We suggest using controlled feeding experiments or longitudinal field investigations to understand claw growth and isotopic equilibration in claw tips. Such information would be valuable in ascertaining whether claw tips can be used in future studies to identify the migratory origins of birds.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, California, United States of America.
authors.forename: John B
authors.initials: JB
authors.lastname: Hopkins
authors.forename: Kyle A
authors.initials: KA
authors.lastname: Cutting
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Warren
mesh_terms: D000818:Animals; D004372:Ducks; D005260:Female; D006724:Hoof and Claw / Q000378:metabolism*; D007554:Isotopes / Q000378:metabolism*; D007633:Keratins / Q000378:metabolism*; D012098:Reproduction
chemical_list: D007554:Isotopes; D007633:Keratins