![]() ![]() ![]() All results are reported for non-exchangeable H expressed in the typical delta notation, in units of per mil ( ‰), and normalized on the Vienna Standard Mean Ocean Water – Standard Light Antarctic Precipitation (VSMOW-SLAP) standard scale.įor δ 13C and δ 15N analyses, between 0.5 and 1.0 mg of feather material was combusted online using a Eurovector 3000 (Milan, Italy - elemental analyzer. Measurement of the two keratin laboratory reference materials (CBS, KHS) corrected for linear instrumental drift were both accurate and precise with typical mean δ 2H ± SD values of –197☐.79 ‰ ( n = 5) and −54.1☐.33 ‰ ( n = 5), respectively. ![]() Hydrogen isotopic measurements were performed on H 2 gas derived from high-temperature (1350☌) flash pyrolysis of 350☑0 ug feather subsamples and keratin standards using continuous-flow isotope-ratio mass spectrometry. The non- exchangeable hydrogen of feathers was determined using the method described by and using two calibrated keratin hydrogen-isotope reference materials. Finally, we contrast the results of multi-isotope assignment with geographic assignments based upon δ 2H alone.Īll feathers were cleaned of surface oils in 2∶1 chloroform:methanol solvent rinse and prepared for δ 2H, δ 13C and δ 15N analysis at the Stable Isotope Laboratory of Environment Canada, Saskatoon, Canada. We then used the triple isotopic ( δ 2H, δ 13C and δ 15N) composition of primary feathers of adult martins returning to their breeding grounds in The Netherlands to provide a first approximation of the most likely regions of Africa in which these feathers were grown by assigning them to isotopic “clusters” in Africa. We conducted a preliminary test of this idea with a comparison of the isotopic composition ( δ 2H, δ 13C and δ 15N) of martin feathers between juvenile and adult birds captured at a single breeding site in The Netherlands over six years. In the absence of wing molt in martins on the breeding grounds, and with molt unlikely to happen during migration, feather replacement takes place at the overwintering sites. Although the suggestion by Carl Linneaus in 1757 (in his academic thesis Migrationes Avium) that swallows and martins hibernate at the bottom of lakes was officially rejected by the Swedish Academy of Sciences in 1854, the wintering distribution of house martins has remained enigmatic. Unlike the closely related barn swallow ( Hirundo rustica), house martins rarely yield recoveries away from their European breeding grounds, despite being widely ringed nor are they frequently observed in Africa (e.g. House martins ( Delichon urbicum) are among the most common migratory aerial insectivores in the Old World, and among the most mysterious with regard to their winter quarters. ![]()
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