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Tennessee Warbler sightings and numbers

Posted on Jan 28, 2014

The Tennessee Warbler (Oreothlypis peregrina) is probably one of those migrants you’re glad to find in either the spring or the fall. It is most often an uncommon treat for the U.S. or Canadian birder as a species that breeds in the boreal forest and can readily blend into the background. Looking at my last five years of eBirding I see only 14 records and half of those came from the last fall season here in and around Chautauqua County, New York. All of the records were of one or two individuals. Suffice it to say it is a tough spot here but this is currently not the case in Costa Rica!

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A Tennessee Warbler by Twan Leenders in Costa Rica, December 2013

Tennessee Warblers winter in Central America, throughout the Caribbean, and in extreme northern parts of South America. That is a tremendous trip for a bird that is about 4-5 inches long and often doesn’t even weigh a dozen grams. After they pass through our backyards the “Tennessees” are concentrated in areas like Costa Rica’s rainforest. Banding season is now over on the Nicoya Peninsula and RTPI Affiliate Sean Graesser, Tyler Christensen and their crew is back in the U.S. Six weeks of hard work at Nicoya Peninsula Avian Research Stations yielded fascinating results pertaining to the species.

As you can read in this blog entry by Tyler the most commonly encountered bird in the final banding session at Curu Wildlife Reserve was the Tennessee Warbler. He writes that “on more than one occasion we would find several in a single net, presumably having been foraging together” which they are apt to do in winter and that “large flocks of Tennessees (up to 60 or 70 individuals) are not an uncommon sight”. That is nothing less than staggering! How many more years have to go by before I see another 60 or 70 individuals total in the U.S.?! Since the species depends somewhat on spruce budworm outbreaks I almost wonder if this was a bit of a bumper year for them, but who knows for sure? This is what such observations on wintering grounds and your own records entered into eBird can help to tell us over time.

Tyler mentions that the numbers provide them with a unique chance to study their appearance, comparing birds of both sexes and different ages and trying to fine tune the team’s identification skills and our collective knowledge. Where else could anyone be afforded such an opportunity? There is still much to learn about their biology and much unknown about so many facets of life of the birds that pass through or live in our yards. When (hopefully!) I see a Tennessee Warbler in a few months I’ll be thinking about this and how it was probably hanging out with dozens of its friends in the tropics during this very cold January. We have a long way to go in fully understanding our birds but we will be working on it every single day of every year.

Scott Kruitbosch
Conservation & Outreach Coordinator

Photo © Twan Leenders