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

<p>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 (<em>Pygoscelis</em> <em>papua</em>), we found that diet-tissue isotopic discrimination factors (Δ³⁴S_diet-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 Δ³⁴S_diet-tissue values. Specifically, Δ³⁴S_diet-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. Δ³⁴S_diet-tissue values obtained for Gentoo Penguins fed a marine fish diet were generally lower than those reported for freshwater-fish-consuming Double-crested Cormorants (<em>Phalacrocorax</em> <em>auritus</em>), the only other bird species in which Δ³⁴S_diet-tissue has been quantified. We found support for the hypothesis that tissue Δ³⁴S_diet-tissue values are inversely related to dietary δ³⁴S values in birds, similar to what has been observed in mammals. Given<span> this relationship, the discrimination factors reported here for </span>Gentoo Penguins <span>may be broadly applicable to other avian species with a similar marine diet.</span> Finally, we provide recommendations for future studies seeking to quantify Δ³⁴S_diet-tissue in avian tissues and guidance to allow for greater application of sulfur stable isotope analysis in ornithological research.</p>