One reason I'm interested, apart from idle curiosity, is the answers directly affect how we approach conservation. The more you know and all that, because knowing is half the battle (leave it to G.I. Joe to turn that into a military action). And now we know a bit more about one of the warbler jewels, one that sadly doesn't breed in my yard. According to recent findings it appears "some individual Cerulean Warblers return to the same wintering area in succeeding years — something we’ve always suspected, but have never proven."
Image courtesy wikipedia.com
This is hopefully an important step forward for this species, one that is of conservation concern throughout its range. From the All About Birds species account,
Cerulean Warbler is one of the species of highest concern in the eastern United States because of a small total population size and significant declines throughout its range. Under consideration for listing under the Endangered Species Act. Listed on the Audubon Watchlist.
Read the Nature Conservancy's account of the report here.