Naturalist Newsletter of January 14, 2008
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
They call the way Donald-Duck laughs, or the way kids make hilarious, halfway rude-sounding squeaks by forcing air from their cheeks past their molars into the backs of their open mouths as they move their lips. Howell describes the voice as "gruff, rasping and rollicking chatters, sheh-eh eh-eh-eh, or cheh- cheh... " but that doesn't come close. They're just funny sounds made all day long in everything from gardens to pine-oak woodland by big Band-backed Wrens, CAMPYLORHYNCHUS ZONATUS.
By "big" I mean up to 8 inches long (20.5 cm) compared to the House Wren's 4-¼ inches (11 cm). Take a brown House Wren, add black-and-white zebra stripes across the back and tail, and bold, black spots on the breast, add a white eye-stripe, almost double the size, and you get a Band-backed Wren.
Band-backed Wrens are common here, and that's OK with me because they cheer up anyplace they happen to be. Like a lot of wrens they're not only noisy but also nosey, unable to contain their curiosity when someone comes down a trail, so they come orbiting around you making their funny sounds.
The genus Campylorhynchus is an important one. The only Campylorhynchus wren in North America is the Southwest Desert's Cactus Wren, which often is the only bird you hear or see when walking through the desert at mid-day. In Mexico we have seven Campylorhynchus species and wherever they occur they're among the most conspicuous of species because of their noisiness and commonness.
When all the Mexican Campylorhynchus species are illustrated on one page you see that they're so similar that you think you'll have trouble in the field distinguishing them but that's not the case. The main reason is that the species are mostly "allopatric," which means that their distribution areas don't overlap. Nearly always in Mexico if you encounter a really big, really noisy, curious wren, it's one of the seven Campylorhynchus species.
Viewing all the Mexican Campylorhynchus distribution maps next to one another you get the strong impression that once there was one mother Campylorhynchus species that fractured into subspecies, and eventually distinct species. Maybe this occurred as one or more ice ages ended and various wren populations moved into and coevolved with ecosystems as they formed.
Band-backed Wrens are distributed from southeastern Mexico to northern Ecuador.
Among the most fun-to-see Campylorhynchus wrens are the Yucatan Wren endemic to the Yucatan's northernmost coast, and the Giant Wren endemic to a narrow band of the Pacific Slope of... Chiapas! The Giant Wren is up to 8.8 inches long (22 cm), compared to our Band- backed's 8 inches, and if I can get down to the coast you can bet that this is one species I'll be looking for.