Cactus wren

The cactus wren (Campylorhynchus brunneicapillus) is a species of wren that is endemic to the deserts of the southwestern United States and northern and central Mexico. It is the state bird of Arizona, and the largest wren in the United States. Its plumage is brown, with black and white spots as markings. It has a distinctive white eyebrow that sweeps to the nape of the neck. The chest is white, whereas the underparts are cinnamon-buff colored. Both sexes appear similar. The tail, as well as flight feathers, are barred in black and white. Their song is a loud raspy chirrup; akin in the description of some ornithologists to the sound of a car engine that will not start. It is well-adapted to its native desert environment, and the birds can meet their water needs from their diet which consists chiefly of insects, but also of some plant matter. The cactus wren is a poor flier and generally forages for food on the ground. Ornithologists generally recognize seven subspecies, with the exact taxonomy under dispute.

Its common name derives from their frequenting desert cactus plants such as the saguaro and cholla, building nests, roosting, and seeking protection from predators among them. Its bulky and globular nests are constructed of plant material and lined with feathers. They do not migrate; instead, they establish and defend the territories around their nests where they live all year-round. It lives in pairs, or as family groups from late spring through winter. Pairing among cactus wrens is monogamous; in each breeding season, the males chiefly build nests, the females incubate eggs, and both parents feed the young.

Populations have declined as the species faces threats related to human activities and habitat loss, although the species remains abundant. Habitat fragmentation and fire have been of particular concern, as the cactus wren is slow to disperse into new habitats. Introduced species have also hurt populations. Feral cats hunt many birds in urban settings, and invasive grasses take up valuable foraging space, reducing habitat size. Despite these threats, the cactus wren has proved adaptable. Cactus wrens have learned to coexist with humans effectively, using human materials and structures for nesting, and even learning to take insects from vehicle radiator grilles. The population still numbers in the millions, leading the International Union for Conservation of Nature to consider the cactus wren a species of least concern.

The wren family is a group of generally small passerine birds, found – with one exception – only in the New World. Although the cactus wren is the largest wren in the U.S., globally the title is shared between the giant wren and the bicolored wren. It was historically considered conspecific (of the same species) with the Yucatan wren and Boucard's wren, but there are numerous morphological and behavioral differences between the species. A 2007 genetic study by Barker indicated that all three were distinct species. Work on wren taxonomy in the 20th century postulated that the Yucatan, Boucard's, and cactus wrens – along with the spotted wren – might constitute a superspecies. The 2007 study showed this to be unlikely, as the cactus wren was found to be ancestral to the other species. Study of the evolution of the cactus wren suggests that it evolved in central Mexico about one million years ago and quickly spread to its modern range.

The first description of a cactus wren was in 1835 by ornithologist Frédéric de Lafresnaye. Lafresnaye was a Frenchman who never visited America; his specimen was gifted to him by ornithologist and businessman Charles Brelay. Brelay procured the specimen from a naval officer who had recently returned from California. It is likely that the bird was picked up at the port of Guaymas, in Sonora. However, Lafresnaye did not know that, and thought the specimen – which he called Picolaptes brunneicapillus – might have come from Peru (far outside the range of the wren), as the officer had stopped there on his journey. The unclear geographic origin contributed to much ensuing taxonomic confusion. Because the original description of the wren had been geographically imprecise, ornithologists described the cactus wren multiple times as different species; incorrect descriptions happened until as late as 1898. Subspecies were also incorrectly described as independent species. Matters were not helped by ornithologist John Gould, who described the cactus wren – as Thryothorus guttatus – independently in 1836 and also failed to say precisely where his specimen had come from. Lafresnaye renamed Gould's find Campylorhynchus guttatus in 1846, still not realizing they had described the same bird. Although ornithologist Spencer Baird suggested in 1864 that Lafresnaye and Gould's birds might be the same, Lafresnayes and Gould's separate descriptions continued to be used until 1945, when it was determined that they were different subspecies of the same bird. The cactus wren was placed in the genus Helodytes by the American Ornithologists' Union in 1894, but they returned it to Campylorhynchus in 1947.

The genus name Campylorhynchus is Greek, and roughly translates to 'curved beak'. The specific epithet brunneicapillus translates as 'brown hair', referring to the bird's brown head and back. The bird's common name comes from its frequent use of cacti as nesting sites, its association with cacti, as well as the use of cacti for perches, roosting, and seeking protection from predators.

The 2007 study by Barker established the relationships between the cactus wren and related wrens in the genus Campylorhynchus, including select subspecies. Those relations are summarized in the following cladogram:

Various subspecies of the cactus wren have been described, and seven are generally recognized. The exact taxonomy of the cactus wren remains under debate, and not all subspecies are universally recognized. Ornithologists Anders and Anne Anderson, in their compendium of 40 years of cactus wren research published in 1973, recognize seven subspecies and do not classify C. b. sandiegensis as an independent subspecies. The International Ornithologists' Union recognizes seven subspecies – including C. b. sandiegensis – but does not recognize C. b. purus. Below are all proposed subspecies: