AN IMMATURE CAVE SWALLOW,
PROBABLY

I entered the cenote via a steep, wooden staircase, the air becoming ever more humid. A feeling for the pit is provided by a picture of the opposite wall below:

The dangling items are the rootlike stems, or stemlike roots of strangler fig trees growing at the rim.

About 15 feet from the platform used by swimmers when they slide into the water a single swallow perched on a tiny ledge beneath a shadowy overhang. Using a flash I got the picture of an immature bird shown below:

When I saw the above image I was struck by how similar the species is to the much more widely distributed and common Cliff Swallow. In fact, because of the black belt beneath the throat I thought it might be that species. Cliff Swallows don't breed here but they do migrate southward through here at this time of year, toward their winter homes in Brazil and Argentina.

However, in Howell's A Guide to The Birds of Mexico and Northern Central America I read that juvenile Cave Swallow chests are washed with duskiness, while no such duskiness is mentioned for juvenile Cliff Swallows. Also, folks here tell me that the same large number of swallows is present year round, so at least I know there's no large influx of migrant Cliff Swallows right now. Therefore I'm calling what's in the picture a juvenile Cave Swallow with maybe 95% certainty, and if I'm wrong I know I'll hear about it.

Cave Swallows display an interesting distribution pattern. A population lives permanently in north-central Mexico, during the summer expanding its northern limits into the nearby southwestern US. In far southern Mexico, in Chiapas, a small, isolated population also visits just for the summer. And then here in the upper Yucatán Peninsula we have another isolated but permanent population.