A Study in Contrasts House Wren — The 21st-Century Caveman

When I used to monitor nestboxes, I would listen carefully as I approached a box, trying to hear what birds were in the area.  One especially bubbly, bouncing song would alert me to potential problems for the other cavity nesters in the vicinity. A 21st-century “troglodyte”—a.k.a. a House Wren—was looking to set up housekeeping.


The plainest of all wrens, the House Wren sports a brown back (sometimes with a hint of cinnamon), a bit of rufous on the rump and at the base of the tail, and a gray-white chest and belly.  The back, wings, and tail display dusky barring. Its tail is often cocked up and its bill is long, thin, and slightly decurved. This active, furtive bird never stays still for long, unless it is singing (usually from an exposed perch).  Although small, a House Wren produces strong vocalizations belying its tiny size. The song is a loud, rapid jumble of notes that warms up with repeated notes, followed by a lively musical roller coaster that rises and falls before it peters out at the end. The wren’s call resembles an irritated stutter—“ch-ch-ch-ch-ch.”  Although House Wrens sing most from March through July, in our neighborhood they start singing again in November.


Breeding in most of Canada and down to the southernmost part of South America, House Wrens occupy the largest span of latitudes of any native passerine (songbird) in the Americas.   House Wren occur widely throughout San Diego County’s coastal slope, although most numerous in oak and riparian woodlands.


House Wrens eat a wide variety of nearly any kind of insect, although they ingest more slow prey (e.g., beetles, earwigs) than they do mobile prey (e.g., flies, leafhoppers).  These obligate insectivores glean small invertebrates in nearly every level of their habitat, from leaf litter or bare ground to all parts of shrubs and trees.


As a cavity nester, the House Wren takes advantage of a wide variety of nest sites. Most frequently, it uses old woodpecker holes, natural cavities, or even small nooks and crannies, especially in coast live oaks and sycamores.  The wren’s spread has followed that of the Nuttall’s Woodpecker, one of the primary excavators of cavities in which House Wrens nest. Really, though, House Wrens can nest in almost any natural or artificial cavity that catches their fancy.  In addition to nestboxes, other human-provided options such as fishing creels, handing flowerpots, old boots, trailer hitches, even a cow skull hanging on a shed can attract a breeding pair. A House Wren clutch generally consists of five or six eggs, incubated only by the female for 12 – 15 days.  Both parents feed the nestlings until they fledge, 15 − 17 days after hatching. Once they leave the nest, the young rely on the parents for food for another two weeks. Some pairs attempt second broods as well.


These little birds have a bad reputation among some people who monitor nestboxes.  House Wrens compete fiercely for nesting sites, pecking and harassing much larger birds, sometimes ejecting eggs and even young nestlings from any nest site they want.  At the same time, though, if they don’t kill your offspring or mate, these feisty little dynamos can serve as helpful neighbors.  Wrens have been known to attack squirrels, weasels, and other nest predators, uttering screeching alarm calls, even as the other birds in the area simply flutter around the area in distress.


The origin of the House Wren’s common name is about as plain as the bird itself.  “House” points out that the bird lives and nests very comfortably around humans; “wren” comes from the Anglo-Saxon wraenna—that language’s name for this type of bird.  In contrast to such a run-of-the-mill common name, though, House Wrens claim one of my favorite scientific names:  Troglodytes aedon.  The species name, aedon, arises from a Greek myth in which Zeus felt sorry for a grief-stricken woman (Aedon) and turned her into a nightingale, renown for its beautiful song.  (Don’t you just hate it when that happens?) This moniker refers to the House Wren’s lilting song. The genus name, Troglodytes, derives from Greek for “one who creeps into holes” or “caveman,” reflecting this wren’s propensity for poking into just about any opening to find insects or check out possible nesting sites.  So House Wrens are indeed 21st-century “cavemen.”


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