North America has 9 swallow species; 6 species breed regularly in Colorado. The common name of “swallow” derives from the Anglo-Saxon “swalewe,” which described this group of birds. These amazing fliers feed almost exclusively on aerial insects. All are insectivores and most arrive Colorado in mid-April, heading back south for the winter by mid-September. Below are brief descriptions of the 4 species Greenwood admits most often: Barn Swallow, Tree Swallow, Violet-green Swallow, and Cliff Swallow.
The Barn Swallow is the most abundant and most widely distributed swallow in the world, found on every continent except Antarctica. For once, the species’s scientific name needs little explanation: Hirundo rustica in Latin literally means “swallow of the country” (where barns abound). A male has a blue-black back; a reddish-orange forehead; and buffy orange chest, belly, and underwings. A female looks similar, although she is paler underneath and has a shorter tail. The Barn Swallow is the only swallow in the U.S. that has a true “swallow tail,” deeply forked and streaming behind. In this photo, you can really see the swallow tail. In the 1800s, this species experienced mass destruction so that those beautiful tail feathers could decorate ladies’ hats. An editorial decrying this practice in Forest and Stream in 1886 led directly to the foundation of the first Audubon Society and to saving this species in the U.S.
Flying equals life for Barn Swallows. They are believed to be the fastest swallow; one was clocked at 46 m.p.h.! Building mud nests fastened to walls or horizontal ledges of just about any structure (we had one build a nest and raise a brood of 4 on our driveway light), nothing says Barn Swallow nest more than feathers, feathers, feathers! (This photo also shows some brand-new hatchlings and a couple of eggs.)
Another species of swallow that Greenwood admits—although all other species fall a distant 2nd to Barn Swallows—is the Tree Swallow. As the first swallows to return to Colorado, they migrate back in early spring when the weather can still be cold and snowy—and flying insects can be hard to find. Luckily, Tree Swallow is the only swallow species that can subsist for extended periods of time on seeds and berries. (In fact, they are among the only species that can digest the waxy outer coating of bayberries—an important fruit in their southern U.S. winter range.) On cool cloudy days, they hunt for insects over ponds; the air over the water is warmer and therefore has more insect activity. Tree Swallows nest in cavities, whether in trees or in human-provided nest boxes. The scientific name—Tachycineta bicolor— is from Greek for “swift mover” (for its speedy flight); the species name is Latin for “two colors (referring to the sharply contrasting colors of the blue-black back and the white belly). You can see this contrast well here.
Closely related to the Tree Swallow, Violet-green Swallows share the same genus. They look much like Tree Swallows too, unless you look carefully and have good light. The male Violet-green has a beautiful violet patch on the rump (also called the “uppertail coverts”), which is often hidden by the folded wings, and a lustrous green back. They are typically the last species to nest in Colorado, arriving in late May and setting up housekeeping by mid-June. Dubbed Tachycineta thalassina, its species name is Latin for “resembling the seas in color. (That seems a bit of stretch; but poetic license is allowed, I suppose.) As with Tree Swallows, Violet-greens are cavity nesters and will readily use nest boxes. Again, feathers are a staple of any Violet-green nest. We happened on a female Violet-green nesting in one of our nest boxes that had so many Band-tailed Pigeon feathers in there, it looked as if she had murdered the bird and stuffed its remains in her box. We called her “The Feather Queen of Box 19.”
Finally, the easiest way to identify an adult Cliff Swallow is by its square tail and orange patch on the rump (uppertail coverts). You get a sense of the tail and uppertail coverts here. Its scientific name, Petrochelidon pyrrhonota, refers to this colorful patch. Petrochelidon means “rock swallow” in Greek, given 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 have a creamy or white strip across their foreheads—sometimes referred to by birders as a “visor.” This visor is obvious here. Males and females look so similar that they can’t be differentiated reliably in the field. But juvenile birds have extremely varied colors and degrees of white speckling on throats and foreheads—greater variation in juvenal plumage than any other species in North America! Their nests are unmistakable—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!). When we were atlasing for the 2nd Colorado Breeding Bird Atlas, my husband and I counted ~450 Cliff Swallow nests on the side of a small bridge across the Arkansas River—meaning roughly 900 adults swallows swooping and swirling over the river, scooping up insects for themselves and their young. Cliff Swallows return to successful nesting sites year after year, refurbishing old nests as needed. You’ve heard of the swallows that return to San Juan Capistrano every year? Yep—they’re Cliff Swallows.
In 2014, Greenwood admitted swallows from all 4 of these species: 49 Barn Swallows (39 nestlings and fledglings, 10 adults); 1 fledgling Tree Swallow; 2 fledgling and 3 adult Violet-green Swallows; and 4 Cliff Swallows (3 babies, 1 adult). Nestlings of most swallow species remain in the nest a long time, compared to other songbirds—at least 20 days after hatching. They have to be 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. The kids soon fly out to meet the parents, who transfer food mid-air. Not long after honing this skill, the youngsters begin to catch insects for themselves, launching into their own, independent lives on the wing.