Many migrant songbird species use high-elevation habitats for stopovers in fall throughout North America, but whether these are good migration habitats as indicated by high fueling rates or other measures has not been previously quantified. At high-quality stopover sites, birds can refuel while maintaining their optimal or preferred migration schedules. We used plasma metabolite analysis to estimate fueling rates of four songbird species during the fall migration period over 3 years at two high-elevation (1,200 m above sea level) and two low-elevation (<25 m above sea level) sites in southwestern British Columbia. For three species with more frugivorous diets during fall—the Fox Sparrow (Passerella iliaca), Golden-crowned Sparrow (Zonotrichia atricapilla), and Hermit Thrush (Catharus guttatus)—estimated fattening rates (defined as residual plasma triglyceride levels) were 37–65% higher at high-elevation sites than at low-elevation sites. By contrast, the largely insectivorous and smaller-bodied Orange-crowned Warbler (Oreothlypis celata) had higher estimated fattening rates at low-elevation sites. We found no elevational differences in plasma beta-hydroxybutyrate or glycerol levels except in Hermit Thrushes, which had lower glycerol levels at high elevation. Estimated fattening rates did not differ among the two sparrows and the Hermit Thrush at high-elevation sites, and all three had higher fattening rates than Orange-crowned Warblers. Our data showing strong elevational differences in residual plasma triglyceride levels support the hypothesis that high elevations can be high-quality stopover habitats and, thus, should be considered for protection in songbird management and conservation plans.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 130 • No. 1