When the Swallows Come Back to Colorado

School’s out, the weather is warm, and we just celebrated Independence Day. Yep, summer’s back again, but above all these the one big thing I’ve begun to associate with summer here in Colorado is the return of the swallow. Colorado boasts 8 swallow species that are here throughout the summer. In the fall they migrate to South and/or Central America to spend the winter. Of those 8 species, probably the most abundant are the cliff swallow (Petrochelidon pyrrhonota) and the barn swallow (Hirundo rustica).

An adult barn swallow. Males are more brilliantly colored than females. Photo by Jamie Simo.
An adult barn swallow. Males are more brilliantly colored than females. Photo by Jamie Simo.
Cliff swallow. https://www.audubon.org/field-guide/bird/cliff-swallow Photo by Greg Lasley/VIREO.
Cliff swallow. https://www.audubon.org/field-guide/bird/cliff-swallow Photo by Greg Lasley/VIREO.

The cliff swallow is a small, chubby swallow with a blue back, rusty neck, and cream-colored belly and inverted triangle above the bill. Its tail is square. The barn swallow is sleeker, but is also blue, rust, and cream. The barn swallow though has a rust-colored inverted triangle above the bill and a distinctive “forked” tail (the fork is due to longer outer tail feathers).

Both cliff swallows and barn swallows can be found all across Colorado. When you sit in your car at a stop light, you may see barn swallows flitting around the cars and large flocks of cliff swallows can often be seen skimming over waterways. In both instances, the birds are hunting for insects, snatching them out of the air while on the wing. Like all insectivorous birds, its the swallow’s diet that mandates migration because insect populations in the United States won’t sustain them through the winter.

Baby barn swallows being fed by a parent. Barn swallows often make use of parking garages for their nests. Photo by Jamie Simo.
Baby barn swallows being fed by a parent. Barn swallows often make use of parking garages for their nests. Photo by Jamie Simo.

Unlike many species, cliff and barn swallows have benefited from human settlement. Swallows originally built their nests on cliffs or canyon walls, but the increase of artificial habitats such as buildings and bridges have allowed the swallows to expand their range. These nests are largely made out of mud, which is cemented to a structure with grass, hair, or feathers packed in. In the case of cliff swallows, these nests are often termed “gourd-shaped.” Because cliff swallows are communal nesters, there can be hundreds of these nests in close proximity. Barn swallows are less communal, often nesting alone or in small groups. Their nests are more cup-shaped.

Old cliff swallow nests attached to a bridge along the Cache la Poudre River. Cliff swallows will usually return to old nesting sites. Photo by Jamie Simo.
Old cliff swallow nests attached to a bridge along the Cache la Poudre River. Cliff swallows will usually return to old nesting sites. Photo by Jamie Simo.

Watching swallows gracefully dive and swoop, chattering to each other the entire time, is an amazing and relaxing pastime and now is the optimal time to see some baby swallows just about to fledge. If you’re in the Denver Metro area you can even get up close and personal with the cliff swallows by taking a canoe trip on the St. Vrain with The River’s Path.

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