Analysis of temporal range change in neotropical passerine migrants using stable hydrogen isotope techniques

Abstract

Avian feathers contain an intrinsic hydrogen isotope signature that indicates the latitude where the feather was grown. When breeding latitudes, determined by analyzing stable hydrogen, are compared between two distinct time periods, changes in range use can be discerned. This technique could prove especially useful for neotropical migrants which are vulnerable to habitat loss and climate change throughout the various portions of the avian life cycle. During migration in 2014, prebasic tail feathers were collected from magnolia warblers by the Powdermill Avian Research Center to determine current breeding latitudes. Prebasic body feathers were collected from study skins of the same species at the Carnegie Museum of Natural History to determine breeding latitudes from 1895-1985. Feather samples were sent to the Stable Isotope Lab at Cornell University for analysis and the resulting isotope data was manipulated using a spatial analyst operation in GIS to model tolerance limits based on an interpolation of stable hydrogen in precipitation. Several comparison models of older feathers and current feathers were created and anova tests suggest the area of occupancy has shifted through time, though the reasons for change may vary. Between urbanization and land conversion for agriculture, the magnolia warbler may be experiencing varying levels of habitat loss along its southern breeding boundary. Changes seen along the northern boundaries are more likely northern colonization in response to climate warming. Nevertheless, the use of stable hydrogen to analyze temporal range change was successful and should continue to be used as a method for detecting range change in threatened or endangered neotropical avian migrants. If a species is shifting over time, natural resource managers could adapt management plans accordingly.