Naturalist Newsletter of December 3, 2007
issued from Yerba Buena Clinic just outside
Pueblo Nuevo Solistahuacan, Chiapas, MÉXICO
about 1740 meters in elevation, ± LAT. 17° 11' 27"N, LONG. -92° 53' 35"W
If you're looking hard for birds, often you don't see woodcreepers. Woodcreepers appear once you're tired out, just gazing blankly into the forest hoping something will flit before you. Then they're like brown leaves the wind silently blows from a shadowy place higher up to a shadowy tree trunk lower down. Woodcreepers aren't flamboyant birds at all. They're like bespectacled, gray-haired clerks in dark, dusty offices in a Dickens novel, just working, working, working at their modest job of gleaning invertebrates from tree-bark fissures, from beneath lichen flecks, from little holes a normal bird might overlook.
No-nonsense Woodcreepers belong to their own family, the Woodcreeper Family, the Dendrocolaptidae, which isn't represented at all in North America or the Old World. It's a strictly neotropical family. Mexico hosts 13 woodcreeper species and they're all reddish-brown birds who climb tree trunks like woodpeckers. Though they're shaped very much like North America's Brown Creepers, Brown Creepers are in an entirely different family. This is a fine example of convergent evolution at work, clear evidence that Nature thinks that a bird who gleans tiny invertebrates from tree trunks ought to be brown and have a certain low-slung shape, and a certain behavior, no matter which family it belongs to.
My list of birds potentially to be seen in upland Chiapas at http://www.backyardnature.net/chiapas/birds-ch.htm lists nine woodcreeper species. Four woodcreeper species have been identified here at Yerba Buena. You can see one of those, the Spotted Woodcreeper, at http://avesphoto.com/WEBSITE/PA/gallery/Gall-8.htm.
In that picture the similarities between North America's Brown Creeper and one of our tropical woodcreepers are obvious. A big difference between them, hard to judge in the photo, is that Brown Creepers are 4.75 inches long while Spotted Woodcreepers are up to 9.5 inches long. Mexico's largest woodcreeper is 12.2 inches long. Our smallest species is only 5.8 inches long, which approaches Brown Creeper size, and from a distance really looks and behaves like a Brown Creeper.
Woodcreepers can be hard to identify. The main differences between them are based on whitish streaking and spotting on their brownish bodies. Usually you must have a good view before you can decide whether the back is really unstreaked, or maybe you're just not seeing the streaks, and the same goes with spotted or not- spotted chests. Once you're familiar with a species you can often recognize it by its voice because woodcreeper voices are fairly distinctive. Howell describes the Spotted Woodcreeper's voice as "A plaintive, descending and slowing series of 2-4... rich, slurred whistles, wheeeoo, wheeeoo, wheeeoo wheeoo..."
The distributions of most of Mexico's woodcreepers continue from here through the tropics at least to Panama and often clear to Argentina. Therefore, once you learn ours you're ready for them when you hit Costa Rica or even the Amazon