"Biologists have recently begun working with a new tool that is a great improvement over the aluminum leg band. Chemical signatures locked in feathers can be read much like a canceled stamp on the outside of an envelope, telling you where the letter originated. These signatures come from naturally occurring patterns of stable isotopes in rainwater that vary predictably across North America. They are transferred up the food web from plants to insects to songbird feathers."
Link: Full Article from Times Argus
Kentucky Warbler image © 2005 Michael Allen McDowell