An exploration of isotopic variability in feathers and claws of Lesser Kestrel Falco naumanni chicks from southern Sicily

Stable isotopes are nowadays commonly used in the study of many key features of avian ecology. However, the adequate choice of what isotopic ratio to consider and what tissues to sample for assessing specific questions may be tricky. Here, we explored the variation in a suite of stable isotope ratios (δ13C, δ15N, δ34S, δ2H, δO) in the feathers and claws of chicks of Lesser Kestrels Falco naumannifrom south-eastern Sicily (Italy) sampled throughout colonies of the same population but surrounded by different habitats. Ouraimsare to provide an insight into the isotopic ecology of Lesser Kestrel and to provide methodological indications for futurestudies.Specifically,we tested whether stable isotope ratios(i)were consistent between feathers and claws; (ii) differed within and between colonies;(iii) reflected differences in surrounding habitats. We found that all isotope ratios significantly differed between claws andfeathers.Hierarchical clusteranalysesrevealedahighconsistencyofstable isotope ratios for alltheelementsbetweensiblingsandnests within thesamecolony. Significant differences instable isotope ratios emerged among colonies and were associated to differences in the surroundinghabitat. The isotope approach has great potential in the study of lesser kestrel ecology, and our results suggest which elementshouldbeselected to approach a set of different ecological questions.