title: Black and white--does melanin change the bulk carbon and nitrogen isotope values of feathers?
abstract: Bird feathers are employed in a wide range of carbon and nitrogen isotope studies relating to diet and migration. Feathers are chemically inert with respect to carbon and nitrogen, after synthesis. It has always been assumed that feathers show isotope values characteristic of keratin, a fibrous structural protein from which they are formed. Little attention has been paid to other components of feathers such as melanin or carotenoids. Melanin is synthesized from tyrosine, which is depleted in both (13)C and (15)N. We compared isotope values of coeval black and white feathers in four different species. Black feather parts were in all cases significantly depleted in (13)C relative to white feather parts but in most species no clear trend was discernable for (15)N. We suggest that additional evaluation may be required to characterize the carbon and nitrogen isotope contribution of feather pigments like carotenoids. Care should be taken in future stable isotope studies when comparing differently coloured feathers.
authors.affiliation: Max-Planck-Institut für Ornithologie, Vogelwarte Radolfzell, Schlossallee 2, 78315 Radolfzell, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Michalik
authors.forename: Rona A R
authors.initials: RA
authors.lastname: McGill
authors.forename: Robert W
authors.initials: RW
authors.lastname: Furness
authors.forename: Till
authors.initials: T
authors.lastname: Eggers
authors.forename: Hendrika J
authors.initials: HJ
authors.lastname: van Noordwijk
authors.forename: Petra
authors.initials: P
authors.lastname: Quillfeldt
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001717:Birds; D002247:Carbon Isotopes / Q000737:chemistry* / Q000378:metabolism; D005241:Feathers / Q000737:chemistry* / Q000378:metabolism; D016014:Linear Models; D013058:Mass Spectrometry / Q000379:methods*; D008543:Melanins / Q000737:chemistry* / Q000378:metabolism; D009587:Nitrogen Isotopes / Q000737:chemistry* / Q000378:metabolism; D010858:Pigmentation; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D008543:Melanins; D009587:Nitrogen Isotopes; D014443:Tyrosine