Causes of bimodal stable isotope signatures in the feathers of a molt-migrant songbird
Stable isotope ratios of hydrogen (δD) and carbon (δ13C) in feathers collected from Painted Buntings (Passerina ciris (L., 1758)) breeding in the midwestern United States
revealed a surprising degree of variation in δD, as well as a clear bimodal signal in δ13C in the innermost primary feather. Because this population does not molt on the breeding grounds, we reasoned that these observations could be due (i) to birds migrating
to two (or possibly more) distinct molting areas or (ii) to differences in the timing of molt (as opposed to molt location) relative to arrival at the stopover site. To evaluate these hypotheses, we collected feathers at a molting location in northwestern Mexico, which revealed
patterns similar to those from the birds in the US (favoring the second hypothesis above). We suspect that some birds arrive at stopover sites and begin molting before their body tissues equilibrate to the new isoscape so that the first feathers grown represent a blend of materials from the
breeding and stopover locations. Other birds may delay molt after arriving at the molting site, allowing them to equilibrate with the local isoscape and produce feathers with isotope signatures of the molting location.
No Supplementary Data
Document Type: Research Article
University of Oklahoma, Center for Spatial Analysis, 101 David L Boren Boulevard, Norman, OK 73019, USA.
University of Oklahoma, Department of Zoology, 111 East Chesapeake Street, Norman, OK 73019, USA.
University of Oklahoma, Oklahoma Biological Survey and Department of Zoology, 111 East Chesapeake Street, Norman, OK 73019, USA.
Burke Museum and Department of Biology, University of Washington, Seattle, WA 98195, USA.
Publication date: 2011-10-16
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