We happened to catch this segment on Scientific American Frontiers, a PBS show hosted by Alan Alda. UMass Amherst biologist Bruce Byers and his colleagues show their fieldwork in a power line clearing in Savoy State Park in western Mass. The show was focused on the "Call of the Wild". In the segment, "Songs of Love and Betrayal":
Alan and Byers attempt to sort out the soap opera-like mating habits of the chestnut-sided warbler.
Only the male chestnut-sided warbler sings, and only during mating season, so the singing seems to be associated with successfully defending a territory and attracting a mate. To check his hypothesis, Byers captures and bands the individuals within one territory. The colored leg bands will help him keep track of which bird is doing what.
