Data from: Sulfur isotopic discrimination factors differ among avian tissues and diets: Insights from a case study in Gentoo Penguins (Pygoscelis papua)

The use of stable isotopes of sulfur (δ34S) to infer avian diets, foraging
habitats, and movements is relatively uncommon, resulting in a lack of
information on patterns of δ34S incorporation in avian tissue. In a
controlled study of Gentoo Penguins (Pygoscelis papua), we found that
diet-tissue isotopic discrimination factors (Δ34Sdiet-tissue) differed
among egg components and feathers synthesized from a common diet, ranging
from -0.4 to -1.7 ‰. We also found that methodical choices such as lipid
extraction and prey tissue selection influenced calculated Δ34Sdiet-tissue
values. Specifically, Δ34Sdiet-tissue values were lower (i.e., more
negative) when calculated using whole fish relative to fish muscle and
lipid-extraction biased egg yolk, but not fish tissue, δ34S values.
Δ34Sdiet-tissue values obtained for Gentoo Penguins fed a marine fish diet
were generally lower than those reported for freshwater-fish-consuming
Double-crested Cormorants (Phalacrocorax auritus), the only other bird
species in which Δ34Sdiet-tissue has been quantified. We found support for
the hypothesis that tissue Δ34Sdiet-tissue values are inversely related to
dietary δ34S values in birds, similar to what has been observed in
mammals. Given this relationship, the discrimination factors reported here
for Gentoo Penguins may be broadly applicable to other avian species with
a similar marine diet. Finally, we provide recommendations for future
studies seeking to quantify Δ34Sdiet-tissue in avian tissues and guidance
to allow for greater application of sulfur stable isotope analysis in
ornithological research.