Sunday, August 20, 2017

Cherrie's and Passerini’s Tanagers

Walking through the grounds of the Villa Lapas eco-lodge in western Costa Rica, we were delighted when an all-black tanager perched on a tree branch in front of us. Then the tanager spun around and displayed its scarlet rump. Aside from being beautiful, Cherrie’s Tanagers are taxonomically interesting. They used to be named Scarlet-rumped Tanagers. But these birds were split into two species— Cherrie’s along the Pacific coast of Costa Rica and Panama and Passerini’s on the Caribbean cost, from southern Mexico to northeastern Panama. 
The males of the two species are virtually identical. The last photo is of a Passerini’s Tanager taken later in our journey in eastern Costa Rica. The dull female Passerini’s Tanagers are actually easier to tell apart. They are brighter in the east than in the west. The two species, however, have different gene sequences. They do not hybridize, even in the only place where they come into contact in northwestern Costa Rica. (Since the males are so difficult to tell apart, I am not sure how ornithologists’ determined that the species don’t interbreed.) Cherrie’s Tanagers are named after George Cherrie, who explored the Brazilian River of Doubt with Theodore Roosevelt in 1913. Passerini was an Italian entomologist who lived in the early 1800s.

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