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Stable isotope profile of autumnal migratory bird feathers on Italian Alps

Citation

Bontempo, Luana et al. (2022), Stable isotope profile of autumnal migratory bird feathers on Italian Alps, Dryad, Dataset, https://doi.org/10.5061/dryad.fn2z34tsk

Abstract

In the study of migration of birds, there are many aspects to be deepened to comprehend both ecology of the species and their geographical connectivity between breeding and wintering grounds. In the last decades, stable isotopes of light elements such as hydrogen, oxygen, nitrogen, carbon and sulphur measured in cheratinous tissues such feathers are increasingly used in order to delineate origin of migrants and to define ecological aspects of birds. Here we present a complete isotopic profile of several passerine species migrating through Italian Alps during post-breeding season. Stable isotope ratios of hydrogen, oxygen, carbon, nitrogen and sulphur were measured in juvenile feathers of 807 individuals of 48 different specie ringed in central Italian Alps during post-breeding migration in the years 2010, 2011, 2012, and 2013. Birds were ringed in two ringing and monitoring stations of Progetto Alpi (http://progetto-alpi.muse.it/). No birds were mistreated, and the sampling took place in compliance with the national and international laws in force at the time of the study.

Methods

Feathers were sampled from migratory birds in two locations on central Italian Alps during the years 2010, 2011, 2012 and 2013. All feathers are juvenile, hence grown in the nest and though carry the natal origin information. The values of δ2H, δ18O, δ13C, δ15N, δ34S were measured for each individual feather. It was possible to determine all five isotope ratios in the majority of individuals, with few values missing. To determine feather δ2H, δ13C, δ15N, δ18O and δ34S values, feathers were first washed in a solvent mixture (diethyl ether-methanol 2:1) and then prepared for analysis (Bontempo et al. 2014). Simultaneous determination of δ13C, δ15N and δ34S (i.e. in the same run) was accomplished using a Vario Isotope Cube isotope ratio mass spectrometer (Elementar, Germany). The δ2H and δ18O values were determined through pyrolysis combustion using a TC/EA (Thermo Finnigan, Bremen, Germany) interfaced with a Delta Plus XP (Thermo Finnigan, Bremen, Germany) continuous-flow isotope-ratio mass spectrometer. Pyrolysis was carried out at 1450°C in a glassy carbon column. The helium carrier flow was 110 ml/min, the GC column was a 1.2 m long molecular sieve 5A, at 110°C. Isotope ratios were expressed in δ-notation against V-PDB (Vienna-Pee Dee Belemnite) for δ13C, Air for δ15N, V-SMOW (Vienna-Standard Mean Ocean Water) for δ2H and δ18O, and V-CDT (Vienna – Canyon Diablo Triolite) for δ34S. The isotopic values of δ2H were calculated using the comparative equilibration approach (Wassenaar and Hobson 2003, 2006) based on the keratin standards CBS (δ2H -197 ‰, δ18O = +3.8 ‰) and KHS (-54.1 ‰, δ18O = +20.3 ‰). Values of δ13C, δ15N and δ34S were calculated against working in-house standards (casein and wheat), which were themselves calibrated against international reference materials using multi-point normalisation: fuel oil NBS-22 (IAEA International Atomic Energy Agency, Vienna, Austria; -30.03 ‰) and sugar IAEA-CH-6 (- 10.45 ‰) for δ13C, L-glutamic acid USGS 40 (-26.39 ‰ and -4.5 ‰ for δ13C and δ15N), hair USGS 42 (δ15N = +8.05 ‰ and δ13C = -21.09 ‰) and USGS 43 (δ15N = +8.44 ‰ and δ13C = -21.28 ‰) for 13C/12C and 15N/14N; USGS 42 (+7.84 ‰) and USGS 43 (+10.46 ‰) for 34S/32S. Values of δ13C were expressed versus V-PDB on a scale normalised against the two reference materials LSVEC (−46.6 ‰) and NBS 19 (+1.95 ‰) (Brand et al. 2014). Values of δ15N were expressed versus Air-N2 on a scale normalised using the two reference materials IAEA-N-1 and USGS32, with consensus values of +0.4 ‰ and +180 ‰ (Brand et al. 2014). Values of δ34S were expressed relative to VCDT on a scale defined by assigning a δ34S value of -0.3 ‰ to the reference material IAEA-S-1. Method uncertainty (calculated as one standard deviation) was 0.1 ‰ for δ13C, 0.2 ‰ for δ15N, 0.3 ‰ for δ18O and δ34S and 2 ‰ for δ2H.

References

Bontempo, L, et al. (2014) Comparison of methods for stable isotope ratio (δ13C, δ15N, δ2H, δ18O) measurements of feathers. Methods Ecol Evol 5: 363–371.

Brand, WA, Coplen, TB, Vogl, J, Rosner, M, Prohaska, T (2014) Assessment of international reference materials for isotope-ratio analysis (IUPAC technical report). Pure Appl Chem 86: 425–467.

Wassenaar, LI, Hobson, KA (2003) Comparative equilibration and online technique for determination of non-exchangeable hydrogen of keratins for use in animal migration studies. Isotopes Environ Health Stud 39: 211–217.

Wassenaar, LI, Hobson, KA (2006) Stable-hydrogen isotope heterogeneity in keratinous material: mass spectrometry and migratory wildlife tissue subsampling strategies. Rapid Commun Mass Spectrom 20: 2505–2510.