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Yves Cherel (Centre d’Etudes Biologiques de Chizé, Villiers-en-Bois, France) and colleagues write in the journal Marine Biology on isotope ratios in mollymawk albatrosses of the genus Thalassarche (and other seabirds).

“Blood and feathers are the most targeted tissues for isotopic investigations in avian ecology, primarily because they can be easily and non-destructively sampled on live individuals.  Comparing blood and feather isotopic ratios can provide valuable information on dietary shifts, trophic specialization and migration patterns, but it requires a good knowledge of the isotopic differences between the two tissues.  Here, δ¹³C and δ¹⁵N values of whole blood (in blood cells of a few species) and simultaneously grown body feathers were measured in seabird chicks to quantify the tissue-related isotopic differences.  Seabirds include 27 populations of 22 wild species that were sampled in 2000–2008, and a review of the literature added 8 groups (including adult birds) to the analysis.  The use of a large data set that overall encompasses wide δ¹³C and δ¹⁵N ranges allowed us to depict for the first time accurate relationships between blood and feather isotopic ratios across avian taxa.  Blood was impoverished in¹³C and generally in¹⁵N compared with feathers.  Both mean δ¹³C and δ¹⁵N values of feathers and blood were highly positively and linearly related [feather δ¹³C = 0.972 (±0.020) blood δ¹³C + 0.962 (±0.414), and feather δ¹⁵N = 1.014 (±0.056) blood + 0.447 (±0.665), respectively; bothP < 0.0001].  The regressions should be applied to mathematically correct feather or whole blood δ¹³C and δ¹⁵N values when comparing isotopic ratios within and between ecological studies on birds.”

Indian Yellow-nosed Albatross with chick, photographed by Peter Ryan

Reference:

Cherel, Y., Jaquemet, S., Maglio, A. & Jaeger, A. 2013.  Differences in δ¹³C and δ¹⁵N values between feathers and blood of seabird chicks: implications for non-invasive isotopic investigations.  Marine Biology DOI 10.1007/s00227-013-2314-5.

John Cooper, ACAP Information Officer, 16 October 2013