INLAND MANGROVE VIREOS

During most walks through the scrub here at least once you hear a buzzy, scolding CHI-CHI-CHI-CHI-CHI birdcall, but you can hardly ever see who is making it. Usually this bird sticks to thick, low cover and moves about a little skulkingly. When he does venture into open space just a glimpse of his small size, yellowish underparts, olive upperparts, white wingbars and short, pointy beak clue you that he's a warbler or a vireo. If you see him well enough to notice his relatively plump shape and sluggish movement, and especially his beak too stout and curved on top to be a warbler's, you know you have a vireo.

He looks a lot like North America's white-wingbarred, yellowish-bottomed vireos except for one thing: The broad areas between his eyes and his beak -- his lores -- are bright, lemony yellow. These yellow lores are very conspicuous, especially since around the eyes there's only a hint of a ring.

It's the Mangrove Vireo, VIREO PALLENS, distributed from Mexico to northwestern Costa Rica. He's found throughout the Yucatan, even in the peninsula's arid center, so by no means, here, is he restricted to coastal mangrove swamps. Most Yucatec Mangrove Vireos live in scrubby woods and overgrown brushy fields exactly like what we have around Sabacché.

This isn't the only bird with "mangrove" in its name to be found here 60 miles inland (100 kms). A Mangrove Cuckoo hangs around a thicket not far from my back door.

Mangrove Vireos occur in two disjunct populations and there's some difference between them. Maybe the most striking divergence is that Pacific Coast birds are indeed found only in coastal mangrove swamps. Why don't Pacific birds range inland the way our Yucatec ones do? Has a genetic mutation in the Yucatan population imparted greater habitat flexibility to our birds?