Excerpts from Jim Conrad's
Naturalist Newsletter

from the March 11, 2006 Newsletter written at Hacienda San Juan Lizárraga one kilometer east of Telchac Pueblo, Yucatán, MÉXICO and issued from Hotel Reef Yucatan 13 kms to the north
BRONZED COWBIRDS ARRIVE
At the hacienda we have three commonly encountered, completely black perching birds: Great-tailed Grackles, Groove-billed Anis and Melodious Blackbirds. The other morning while sitting next to my breakfast campfire I saw three black birds land in a nearby Neem tree and they did not behave like any of those three, common, black species.

For, suddenly one of the birds rose on his spindly legs, spread his wings, puffed out his body especially in his neck area, and approached one of his companions slowly pumping his torso up and down. Unable to defend myself from a flash of anthropomorphism, the image evoked was that of a pervert with his black overcoat opened wide to reveal his naked body, tiptoeing and lewdly thrusting his pelvis as he approached his victim.

When the bird turned his head in a certain direction and I saw that his eyes were bright red, I knew that the black-overcoat image wasn't as absurd as it might seem. For, this was a Bronzed Cowbird, sometimes known as the Red-eyed Cowbird. And like its northern relative the Brown-headed Cowbird, this bird is a "brood parasite." The female lays her eggs in the nests of a wide variety of other bird species, which then incubate the cowbird's eggs and raise the nestlings to maturity, often to the detriment of their own nestlings. You can see a Bronzed Cowbird at http://www.mbr-pwrc.usgs.gov/id/htmsl/h4960pi.jpg.

Bronzed Cowbirds are distributed from southern Texas and New Mexico through Mexico to El Salvador and Honduras. The North's Brown-headed Cowbird makes it to central Mexico, but not to here.

I read that during the winter Bronzed Cowbirds join into large flocks with other blackbirds but that during the rest of the year they travel singly or in small groups. Maybe what I'm seeing now is a wandering small group after the winter flock has broken up. All three, which hung around all week, are males, so maybe they're "scouting" before females arrive. At first they never sang, but now rarely you hear a quick, subdued squeal a lot like the Brown-headed Cowbird's.

Maybe this is the first hint of our birdlife readying itself for the rainy season, for other bird species are subtly changing their behaviors as well. The White-wing Doves are cooing much more exuberantly than usual. Little Ruddy Ground-doves regularly do combat upon the stone walls -- though they appear to nest all winter, so I'd not expect much of a change in them. Two months ago I watched a mother Ruddy Ground-dove defend her nest heroically against four Yucatan Jays who uncoordinatedly approached her nest from all directions, apparently hoping for an egg or nestling meal. Tropical Mockingbirds sing more vociferously than usual and during my campfire breakfasts each morning the Southern House Wrens more vigorously than I remember chortle, warble and trill their songs, sometimes atop rocks just a few feet away.

Maybe for some bird species the deal is this: Courtship now leads to nestlings just as the rainy season returns in May, when bugs will be abundant again. Maybe the Bronzed Cowbirds have arrived in preparation for that ample nesting time.