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.

5 thoughts on “When the Swallows Come Back to Colorado”

    1. Hi Carol, I’m assuming the swallows you have are Barn Swallows. Are they building in an inconvenient place? Barn Swallows aren’t communal nesters so, though they may nest close to each other, they don’t seek out others of their kind to nest near. I came across this site where you can buy an artificial nest cup. I’ve never tried it, so I don’t know how well it would work, but you might put one of these up in a place you don’t mind the swallows nesting. It could divert the swallows to this nest rather than where you don’t want them. Good luck!

      https://www.thebirdhousechick.com/products/barn-swallow-nest-cups-set-of-2

  1. We have been watching what we think are swallows; black and white dive bombers and flighty with a blue iridescence.
    They set up home in a birdhouse we had hanging and nested all of June it appeared. Two weeks ago we started hearing little peeps and have enjoyed watching the parents feed and most recently have been blessed to see little beaks open and fed. They seem to be braver and are hanging 1/2 way out of house now and surely are about ready to leave the nest…However, there are now up to 6 adults flying at the birdhouse and we fear they are invaders to eat or hurt babies. Parents are on guard alot but leave them unattended! Is it normal to have a communal feeding group as they are about to fly?

  2. Hi Mary, sorry to get back to you so late. They definitely sound like Tree Swallows to me. I haven’t heard about communal feeding. Was there only one nesting pair? It could be that there were a lot of flying insects around the nest box that the other swallows were trying to take advantage of. How did things turn out? Did the babies fledge successfully?

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