Naturalist Newsletter of May 29, 2008
issued from Mexico's Southernmost State, CHIAPAS
The most commonly seen birds are House Sparrows, Pigeons and Great-tailed Grackles. At the crack of dawn House Sparrows outside my pension door made a tremendous racket.
Throughout most of the day but especially in early mornings you hear high-pitched, downward-slurring TSEEEEW calls. The callers are such quick, nervous little shadows that it can take awhile to figure out who they are. They're Rufous-collared Sparrows, ZONOTRICHIA CAPENSIS, sometimes known as Andean Sparrows, high-elevation and similar-looking cousins to North America's White-throated and White-crowned Sparrows.
Mostly San Crisóbal's Rufous-collared Sparrows stay hidden inside trees or atop flat roofs, but sometimes a little flurry of them blows around a building corner and lands in the grass, or they perch for a second on a gutter or the top of a red-tiled roof, and then you can admire their richly rufous cape, white throat and bold back-striping. Some birds have learned to be park birds, hopping around like House Sparrows, apparently pecking crumbs of dropped tostados or what's left after Pigeons eat bread tossed to them by tourists.
It's interesting that though Rufous-collared Sparrows are distributed from Chiapas all the way south to Tierra del Fuego, and they're found in environments ranging from towns to very wild high elevations (up to 11,500 ft, 3500 m), in Mexico the species occurs only in Chiapas. You'd think that such a wide ranging species capable of living in so many environments would have spread across the lowland Isthmus of Tehuantepec separating Chiapas from mainland Mexico, but for some reason that just hasn't happened.
Especially in early mornings on sunny days male House Finches sing their high-pitched, varied, rich warbles from San Cristóbal's park trees. Though in other places I've seen them close to the ground, here they stay pretty high. Boxelders and ash trees in parks at this time of year are heavy with winged fruits so I expect it's a good time to be a House Finch. House Finches are common permanent residents in nearly all of upland Mexico on the mainland side of the Isthmus of Tehuantepec, but on this side they occupy just a small, isolated population centered around Tuxtla Gutierez and San Cristóbal. Howell suggests that these birds may derive from escaped caged birds, for often they are indeed caged by people who appreciate their pretty singing and the male's red head and chest.
Soaring over large plazas fronting big churches regularly you see small flocks of Northern Rough- winged Swallows, which are permanent residents here. They're easy to recognize because of their only slightly cleft tails and dingy throats.
Sometimes mixed in with the Rough-wingeds you spot a Barn Swallow, distinct with its very deeply forked tail and dark cinnamon throat. In most of Mexico Barn Swallows are strictly migrants or winter visitors, except in the central highlands around Mexico City where they're permanent. Howell's distribution map shows them as being only winter residents in the Chiapas highlands, but last Saturday I got a good view of a Barn Swallow tending a nest stuck on an adobe wall right beneath a red-tile roof eve, so maybe something new is going on with Barn Swallows here.
I saw a hummingbird in a park but couldn't identify it.