title: Differences in the stable isotope signatures of seabird egg membrane and albumen--implications for non-invasive studies.
abstract: In many bird species, egg membranes can be obtained non-invasively after the chicks have hatched, and stable isotope analysis of egg membranes can be used to study the diet and foraging distribution of these birds during egg formation. It has been suggested that the enrichment factors of albumen and egg membranes differ for 13C, but are similar for 15N. In this study, we compared carbon and nitrogen stable isotopes of the membranes and albumen of individual eggs of three wild seabird species, the Southern Rockhopper penguin Eudyptes chrysocome, the Imperial shag Phalacrocorax atriceps albiventer, and the Thin-billed prion Pachyptila belcheri. We also included chicken eggs for comparison. Egg membranes were generally enriched in 13C, compared with albumen. The difference varied between species, with 2.1 per thousand in Rockhopper penguins, 1.6 per thousand in Imperial shags, but only 0.5 per thousand in Thin-billed prions and 0.4 per thousand in chicken eggs. Egg membranes were slightly enriched in 15N in Imperial shags (0.9 per thousand) and chickens (0.5 per thousand), compared with albumen, while there was no difference for Thin-billed prions and Rockhopper penguins. The isotopic values of carbon and nitrogen were correlated between albumen and egg membranes of individual eggs, suggesting that egg membranes can be used reliably to investigate trophic differences between individuals, seasons or colonies. Species-specific mathematical corrections could be used to compare results across studies that use different egg components.
authors.affiliation: Max-Planck-Institut für Ornithologie, Vogelwarte Radolfzell, Schlossallee 2, 78315 Radolfzell, Germany. petra.quillfeldt@gmx.de
authors.forename: Petra
authors.initials: P
authors.lastname: Quillfeldt
authors.forename: Rona A R
authors.initials: RA
authors.lastname: McGill
authors.forename: Juan F
authors.initials: JF
authors.lastname: Masello
authors.forename: Maud
authors.initials: M
authors.lastname: Poisbleau
authors.forename: Hendrika
authors.initials: H
authors.lastname: van Noordwijk
authors.forename: Laurent
authors.initials: L
authors.lastname: Demongin
authors.forename: Robert W
authors.initials: RW
authors.lastname: Furness
mesh_terms: D000418:Albumins / Q000737:chemistry*; D000818:Animals; D001717:Birds; D002247:Carbon Isotopes / Q000032:analysis*; D002645:Chickens; D004531:Eggs / Q000032:analysis*; D005321:Extraembryonic Membranes / Q000737:chemistry*; D013058:Mass Spectrometry; D009587:Nitrogen Isotopes / Q000032:analysis*; D009792:Oceans and Seas; D046429:Spheniscidae
chemical_list: D000418:Albumins; D002247:Carbon Isotopes; D009587:Nitrogen Isotopes