On the wild side—June, 2011
by Tina Mitchell
Six species of swallows breed in Colorado: Bank, Barn, Cliff, Northern Rough-winged, Tree, and Violet-green. Arriving in Colorado in early May and heading back south for the winter by mid-September, 2 species are the most common in our area: Cliff Swallows and Violet-green Swallows.
To identify an adult Cliff Swallow, look for a square tail and an orange patch on the rump (also called the “overtail coverts”). Its scientific name, Petrochelidon pyrrhonota, refers to this colorful patch. Petrochelidon means “rock swallow” in Greek, giving a nod to its nesting sites among cliffs and rocks. The species name, pyrrhonota,means “flame-colored back” in Greek. Cliff Swallows also have chestnut-colored throats and most show a creamy or white patch across their foreheads—sometimes referred to as a “visor.” Males and females look so similar that they can’t be differentiated reliably in the field. Their nests are unmistakable, though—gourd-shaped bowls covered with mud pellets, attached to a vertical surface (often a bridge over a river or a wall of a building), with a small entrance tunnel. Nests are usually placed very close together and under an overhang to avoid heavy rains (which could be disastrous for mud homes!). You can see a colony of Cliff Swallow nests under the roof overhang on the Coaldale Firehouse and along the sides of the Vallie Bridge. (When we were atlasing for the Colorado Breeding Bird Atlas in 2007, we counted approximately 450 active nests on Vallie Bridge alone!) Cliff Swallows return to successful nesting sites year after year, refurbishing old nests as needed. You’ve heard of the swallows returning to Capistrano every year? Yep—they’re Cliff Swallows.
As with the Cliff Swallow, Violet-green Swallows don’t have the classic long, forked “swallowtail” either. (In the U.S., the only swallow that has this tail shape is the Barn Swallow.) In less-than-perfect light, Violet-green Swallows have dark backs and sharply contrasting white bellies. Flying, they flash a bit of white on the back at each side of the tail—sometimes called “saddle bags.” In perfect light, the male Violet-green has a beautiful violet patch on the overtail coverts, often hidden at rest by the folded wings; violet on the upper wings; and lustrous green backs. Females are much drabber, looking basically brown on the back and white underneath. Typically the last swallow species to nest in Colorado, they arrive in mid-May and set up housekeeping by early June. Dubbed Tachycineta thalassina, their genus name derives from Greek for “swift mover;” the species name comes from Latin for “resembling the seas in color” (seems a bit of stretch, but poetic license is allowed, I suppose). Violet-greens are cavity nesters and will easily use human-constructed nestboxes. Last year, we hosted 21 nesting pairs of Violet-greens in our nestboxes. Their ubiquitous pre-dawn chatter as they chased down breakfast for both themselves and their scores and scores of nestlings became the early dawn song of summer at our house.
The common name of “swallow” comes from the Anglo-Saxon “swalewe,” which described this group of birds. Flight equals life for these birds. These amazing aerialists feed almost exclusively on flying insects. Young swallows remain in the nest quite a long time, compared to most songbirds—about 20 days after hatching, compared with ~14 – 15 days for many other species. They have to be pretty decent flyers as soon as they fledge, so they need the extra days to develop good flight muscles. The parents feed the fledglings for about a week after they leave the nest, teaching the youngsters to catch insects for themselves and launching them into their own, independent lives on the wing.
Thanks to Wikimedia Common for the great photos!