The Wrens of Colorado

Quick! What’s that dull-colored little bird with the Napoleon complex? Is it holding its tail upright? Is it giving you the side-eye and scolding you with some truly acrobatic vocals? Well, my friend, you probably have the Joe Pesci of the bird world on your hands: the wren.

There are over 80 species of wrens world-wide, with most of them occurring in the western hemisphere. In Colorado, there are 5 that can be regularly found and several rarities that show up on occasion, but here I’ll concentrate on the more common ones.

House Wren at Sylvan Lake State Park in Eagle, CO building a nest near one of the cabins. Photo by Jamie Simo.

The most common wren to most people along the Front Range is probably the House Wren (Troglodytes aedon), which is a summer resident in Colorado and is named for its tendency to nest in proximity to houses. House Wrens are one of the smallest wrens in Colorado at about 4.5 to 5 inches. They are also the drabbest. They love to hang out low in brushy areas where their plain, faintly barred, brown coloring blends in well.

House Wrens are an interesting species with a mixed reputation. The males have a beautiful song they use to attract mates and defend their territory. They’re also industrious. Once he has an interested lady, a male House Wren will bring her around to a number of cavities where he has built up a nest base of sticks. She’ll then pick one to complete a nest with grasses, fur, and other soft materials. House Wrens are particularly aggressive during the nesting season. They will pierce the eggs of other birds nesting nearby (including bluebirds).

Marsh Wren at Jim Hamm Natural Area in Longmont, CO. Photo by Jamie Simo.

About the same size as the House Wren is the Marsh Wren (Cistothorus palustris), also a summer resident throughout most of Colorado. Like its name, the Marsh Wren is found in wetland areas where it slinks around among cattails and reeds, flying only short distances with its diminutive wings. The male’s song sounds to me a lot like a VHS being rewound or fast-forwarded. Marsh Wrens are brown, but with a more visible pale eyebrow and paler underparts than the House Wren. They also have a black and white striped patch on their back.

Like the House Wren, the Marsh Wren male builds multiple “dummy” nests that he will show his mate for her to choose between. Unlike House Wrens, however, Marsh Wrens don’t nest in cavities. Their nests are dome-shaped and formed from grasses, reeds, and other marsh plants. Marsh Wren males will mate with multiple females in an area and both parents will defend the resources of that area by destroying other birds’ eggs and killing nestlings.

Bewick’s Wren at Lake Pueblo State Park in Pueblo, CO. Photo by Jamie Simo.

In the southern and western portions of Colorado lives the Bewick’s Wren (Thryomanes bewickii) whose body is only slightly bigger than a House or Marsh Wren’s, but whose tail is much longer and white-edged. Bewick’s Wrens have a very prominent white eyebrow, pale underparts, and a decurved (down-curving) bill. The Bewick’s Wren prefers dry, scrubby areas in woodlands or grasslands.

As with the House Wren, Bewick’s Wrens nest in cavities, which unfortunately has put them in direct competition with the House Wren as the House Wren’s range has expanded with human settlement. Though smaller, the House Wren is fiercer and out-competes the Bewick’s Wren, which has all but been eradicated from the eastern United States and is in decline in the west.

Canyon Wren at Golden Gate Canyon State Park in Golden, CO. Photo by Jamie Simo.

If you’re in a rocky area with cliffs, you may encounter the chubby little Canyon Wren (Catherpes mexicanus) with its long, decurved bill. Quite flashy for a wren, it has a rust-colored body with black and white speckles and a stark white throat. You’re more likely to hear this wren than see it, however. The male’s song descends as if he’s falling down a cliff. There’s some speculation within the birding community that the female also sings, though a raspier, more ascending song.

Canyon Wrens nest in rock crevices where they build their cup nests. Because they’re able to pick insects out from between rocks with their long beaks, they are mostly year-round residents in Colorado rather than migratory. Due to the steepness and rockiness of their habitat, Canyon Wrens haven’t been studied as much as some of their cousins. They are the only species in their genus.

Rock Wren at Barr Lake State Park in Brighton, CO. Photo by Jamie Simo.

Last, but not least, the Rock Wren (Salpinctes obsoletus) is the largest wren in Colorado, though it’s only slightly larger than the Canyon Wren. It’s also probably my favorite wren in Colorado because it’s just so charismatic with its deep knee bends and curious mien. This bird is greyish-brown with faint speckling on its upper parts, buffy belly, and pale, buffy eyebrow.

Like the Canyon Wren, Rock Wrens are mostly found in rocky areas like canyons. This comes in handy in the nesting season because they incorporate the rocks into their nest site. The cup nest of the Rock Wren is built in a crevice by the female and then both sexes will seek out and lay a series of flat stones in front of the nest crevice to form what scientists often refer to as a “front porch.” What the purpose of this “porch” is though isn’t known.

So, that’s it! Which wren are you watching right now? Or maybe the question should be: which wren is watching you?