Naturalist Newsletter of May 12, 2008
written in the community of 28 de Junio, in the Central Valley,
8 kms east of Pujiltic, Chiapas, MÉXICO
about 800 meters in elevation, ± LAT. 16° 18'N, LONG. -92° 28'W.
For the last couple of weeks during early morning hours when it was still cool but the sun was shining brightly I've heard bobwhites calling, hu-WHEET! hu- WHEET! Or bob-WHITE! To my ears the calls are identical to those heard in fields up North.
However, if you're lucky enough to spot a male you can see that this bird looks very different from the bobwhites heard up north. Northern Bobwhites are white-throated and have white eye-stripes, and their sides and chests are heavily spotted. Male bobwhite heads down here are totally black except for the white eye-stripe, and their underparts are solidly cinnamon- rufous.
Despite the big difference in looks, it turns out that our bobwhites are the very same species found up North, the Northern Bobwhite, COLINUS VIRGINIANUS. Here is a bird with a huge distribution. The bird's advancement across the continent probably was helped when humans converted North America's forests to broad open areas producing lots of weed seeds, which is the Bobwhite's habitat.
Our birds being members of the same species accounts for their calling like the northern ones, but how come ours look so different from the northern ones?
It turns out that in Mexico four Northern Bobwhite subspecies groups are recognized: texanus in the northeast; graysoni in central Mexico; pectoralis along the Atlantic Slope and disjunctly in south-central Mexico, and; coyolcos on the Pacific Slope south and inland to here and northwestern Guatemala.
You might remember that in the Yucatan we had the Yucatan Bobwhite, Colinus nigrogularis. Some say that the Yucatan Bobwhite is just another subspecies of the Northern Bobwhite while others insist that it's a full species all by itself. Being a full-blown species implies that the Yucatan Bobwhite population is for the most part reproductively isolated from the rest of the Northern Bobwhite gene pool. In contrast, genes flow among the four subspecies, so that often where distributions meet birds appear with intermediate features.
It's all evolution in progress. The current Bobwhite taxonomical situation presents a snapshot of one big species fracturing into several subspecies, and maybe one of those subspecies already has crossed the threshold to reproductive isolation, and is a full species.
If you could see our black-headed, rufous-cinnamon-bellied bobwhites you might think that our subspecies already is different enough to be considered a separate species. However, when you hear that crystalline hu-WHEET! Hu-WHEET! on a sunny morning, you know it can't be anything other than the pure bobwhite of the northern countryside.