Around the sunlight-dazzled, windswept, ridge-crest town of Cuatro Palos, all afternoon, Western Bluebirds glided from one maguey plant to another. In the intense light they looked all-black, but sometimes when one turned just right you could catch a glimpse of chestnut on the chest and sometimes even see a glimmer of blue. However, it wasn't necessary to see the birds' colors to know them, for bluebirds have that special, low-swooping, soft-touch manner of flying from one perch to another, or from a perch onto the ground for a quick snack, and there among the heights their flight seemed even more distinctive.
Western Bluebirds look a lot like their Eastern counterparts, just with less rustiness on their chests, and their throats are blue, not rusty as with the Easterns. Up north the two species occupy different sides of the continent but down here the species mingle in the uplands, occupying similar habitats. It's interesting that both species avoid the hot, humid lowlands.
At this time of year the birds' hormonal levels are low so they're not territorial and often appear in small groups. Both the Eastern and Western species are permanent residents here, though during the winter their numbers may be augmented by migrants from the north. The Westerns seem most common here, however. Well, their scientific name is SIALIA MEXICANA, after all.
The Mountain Bluebird, with a paler, sky-blue color, also occurs in the northern Mexican uplands, but only as a winter migrant.