Dr. Charles van Riper III

Professor, School of Natural Resources and the Environment
USGS Research Scientist Emeritus  

Sonoran Desert Research Station
125 Biological Sciences East ~ University of Arizona ~Tucson, AZ 85721-125
(520) 626-7027 ~ (520) 670-5100 fax ~ (520) 491-0721 call

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Migratory Corridors

Determining the temporal and spatial patterns of migration and the degree of population segregation during migration is critical to understanding the ecology and evolution of migration as well as long-term population trends of migrant birds. Whether breeding populations differ in migration routes or times could suggest different source of selection and require alternative management approaches. To better understand migration patterns, we have incorporated two distinct techniques to determine where, when, and how birds are returning to breeding grounds.  
Radio Tracking (Protocol) – Over the last several years we have been attempting to isolate migration corridors by radio tracking select birds on their way back to their breeding grounds. During the day, we capture birds and fix a small radio on their back. We then attempt to follow each individual through the night as it moves from one stopover location to the next. By following the specific path individuals are using as they return to breeding grounds, we hope to better understand the evolution of migratory behaviors and identify important migration corridors. 
Stable Isotopes (protocol) – In addition to looking at individual migration behaviors, we are also attempting to understand broad patterns across populations. Recent studies have shown that stable hydrogen isotopes are a powerful research tool for identifying where individuals procure resources to allocate to molt. Hydrogen isotopes differ across latitudes, and by looking at the isotopes in an individual’s feathers, we can identify the location where that individual was when it produced that feather. By choosing species that molt on their breeding grounds we are able to identify the breeding locations of returning migrants (Paxton et al. 2006).





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