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Mesoscale patterns of altitudinal tenancy in migratory wood warblers inferred from stable carbon isotopes
Author(s) -
Graves Gary R.,
Romanek Christopher S.
Publication year - 2009
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.1890/08-0934.1
Subject(s) - altitude (triangle) , isotopes of carbon , ecology , context (archaeology) , seasonal breeder , δ13c , biology , habitat , stable isotope ratio , total organic carbon , paleontology , physics , geometry , mathematics , quantum mechanics
We analyzed carbon isotope ratios (δ 13 C) of liver and pectoral muscle of Black‐throated Blue Warblers ( Dendroica caerulescens ) to provide a mesoscale perspective on altitudinal tenancy in the Appalachian Mountains, North Carolina, USA. Movements of males are poorly understood, particularly the degree to which yearlings (first breeding season) and older males (second or later breeding season) wander altitudinally during the breeding season. Liver and muscle δ 13 C values of warblers exhibited significant year and altitude effects, but yearling and older males were isotopically indistinguishable. Liver δ 13 C values increased with altitude at the rate of ∼0.5‰ per 1000 m. The altitudinal lapse rate of muscle δ 13 C (∼1.1‰ per 1000 m) was nearly identical to the average rate of increase reported in several groups of C 3 plants (∼1.1‰ per 1000 m). This suggests that the majority of males foraged within relatively narrow altitudinal zones during the breeding season. We caution, however, that the discrimination of altitudinal trends in carbon isotope ratios depends on relatively large multiyear samples. Given the scatter in data, it is unlikely that individuals can be accurately assigned to a particular altitude from carbon isotope values. Rapid adjustment of liver and muscle δ 13 C values to local altitudinal environments is consistent with the results of experimental dietary studies that show carbon turnover rates are relatively rapid in small migratory passerines. In a broader context, carbon isotope data have been increasingly used as proxies for wintering habitat use of Nearctic–Neotropical migratory passerines. However, tissues with high metabolic rates are unlikely to retain much isotopic signal of wintering habitat use by the time migrants reach their breeding territories.