Blackpoll Warbler at Aquiares

Blackpoll Warbler (Setophaga striata): Reinita Rayada; Paruline rayée; Streifenwaldsänger

We’re in the middle of migration season in Costa Rica, and this can often bring surprises. To many North American readers this pretty little warbler will be readily familiar, but in Costa Rica it’s considered a rare migrant. In migration it makes one of the longest non-stop flights over water ever recorded for any songbird, averaging 2,500 km – according to Avibase – The World Database. When the Blackpoll Warbler leaves the shores of continental (mostly eastern) North America, it heads out over the Atlantic/Caribbean for north-eastern South America, which accounts for the scarcity of recordings in Costa Rica. I myself have never identified one here.

Friends and contributors John and Larry live right by the Aquiares coffee fields, a location which is also close to my own village of San Antonio. Aquiares is fast becoming one of the top birding destinations in the Turrialba area and is where John with his usual tireless persistence took the following photos of what is probably a juvenile female of the species.

Immature Blackpoll Warbler at the Aquiares lagunita, near Turrialba; photo by John Beer

This individual has stayed faithful to this location since at least January 23. The quality of these images has allowed the careful identification that is needed to separate this immature warbler from the immatures of other migrant warblers of the Setophaga genus, several of which, the Bay-breasted Warbler (Setophaga) for instance, are quite commonly encountered in Costa Rica. Check your field guide and be prepared to get confused if you can’t get a very close look!

The same immature Blackpoll Warbler individual, but with a clearer view of the underparts; photo by John Beer.

For comparison purposes the next photograph shows a Blackpoll Warbler of similar plumage in late September migration (2018) in Minnesota, where Larry avoids the summer heat of the tropics. Blackpolls do not breed in Minnesota and are also uncommon during fall migration. Note here the more extensive yellow colour and the lack of white above the eye. This individual seems to be an adult female and was photographed, perhaps unusually, on the ground:

Blackpoll Warbler in Minnesota, perhaps an adult female; photo by Larry Waddell.

By the way, Blackpolls returning north in spring migrate via the Caribbean and not over open water. This would perhaps suggest that we should have more sightings in spring than in autumn. I’m glad I’m not the one trying to make precise identifications of these ‘confusing fall warblers’, as they have often been termed. Male Blackpoll Warblers in their contrasting black-and-white breeding plumage present much less of an identification problem. If we find one locally in our area, I’ll be sure to add a post and photographs immediately – not much chance, I’d say, since I can find no photographs taken here of breeding-plumage males. But this is Costa Rica and you never know!

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