Cerulean Warblers Return to the Same Winter Habitat

Since I adopted the Cerulean Warbler as my blog's mascot, I try to keep abreast of news regarding the species. The tiny warbler has been rapidly declining in recent years thanks partly to the loss of mature forest breeding habitat to mountaintop removal mining and other developments and partly to the loss of 64% of its winter habitat. While the decline has not been sufficient to get it listed under the Endangered Species Act, this warbler has been the focus of intense research on this continent and in its winter range in South America.

Through the Nature Conservancy's blog, I learned of an interesting finding from a research station in Colombia's Andes Mountains: some Cerulean Warblers return to the same wintering grounds year after year.

This research is so exciting that every time I read the reports, I immediately want to head to the field to help out. Gabriel and his team have, since 2003, captured 49 individual Cerulean Warblers. They have used an innovative technique with aerial mist nets suspended on bamboo poles high in the canopy, which is what you have to do to capture this species. Most incredible, the team has recaptured 4 of these birds in different wintering seasons.

This has demonstrated, I believe for the first time, that some individual Cerulean Warblers return to the same wintering area in succeeding years — something we’ve always suspected, but have never proven. So you can meet some of the characters, on the left is a photo of a female Cerulean named Aleja, who was caught and banded in March, 2009. You can see some of the color bands that were placed on her, so she could be followed to study her behavior and diet.

The implications of this finding for conservation will be up to the researchers in the field to determine. However, I would like to suggest a few areas where it might be relevant. First, if individual birds return reliably to the same winter locations, it makes preserving the habitat at those locations all the more important. This is something where U.S. nonprofits can be of some assistance. Second, maintaining (and possibly expanding) these wintering areas will be easier if there is some incentive to keep them forested. One way to do that is through encouraging shade coffee production, which benefits Cerulean Warblers and other species. U.S. consumers (especially birders) can play a role here by providing a market for it. Finally, if warblers return consistently to the same breeding grounds and the same wintering grounds, chances are that they do the same for at least some migration stops. In that light, keeping migrationg stop-overs – even small ones – intact ought to be a major benefit.

(Photos: Top photo by Flickr user Petroglyph; second photo included in the linked blog post.)