Cactus wren
The cactus wren 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.
Taxonomy and systematics
The wren family is a group of generally small passerine birds, foundwith one exceptiononly 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 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 wrensalong with the spotted wrenmight 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 specimenwhich he called Picolaptes brunneicapillusmight have come from Peru, 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 wrenas Thryothorus guttatusindependently 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:
Subspecies
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 subspeciesincluding C. b. sandiegensisbut does not recognize C. b. purus. Below are all proposed subspecies:- C. b. brunneicapillus – the nominate subspecies. Its range is northern Mexico in the states of Sonora and Sinaloa. Its distinction from other subspecies is enhanced by its pure white chin.
- C. b. guttatus – found in central and southern Mexico. It is duller and more gray than the nominate subspecies; its upper parts also have less noticeable white markings. Guttatus means 'speckled' in Latin.
- C. b. affinis – found in southern Baja California. Its underparts are paler, and it has fewer black marks than the nominate subspecies. Its rectrices, excluding the middle pair, have white bars. C. b. affinis tends to lay fewer eggs than other subspecies, generally two at a time instead of the more typical three to five, and its eggs are notably paler than those of other subspecies. Affinis means 'allied' or 'related' in Latin.
- C. b. couesi – covers most of the cactus wren's range in the southern United States, including Nevada, Utah, Arizona, New Mexico, and Texas, as well as the Mexican states of Sonora and Chihuahua. The American Ornithological Society classifies all Californian subspecies as C. b. couesi. It is larger than the nominate subspecies and has paler underparts. It is sometimes referred to as C. b. anthonyi, but C. b. couesi takes precedence. This subspecies is named for army surgeon and ornithologist Elliott Coues.
- C. b. bryanti – found along the western coast of Baja California, separated from the range of C. b. couesi by at least. C. b. bryanti has notable white markings on the rump and scapulars. Its upperparts are darker and more brown than those of the nominate subspecies. It is named for Californian ornithologist Walter Pierce Bryant.
- C. b. purus – present on the eastern and western coasts of Baja California. Its underparts are almost pure white, and its flanks are notably less cinnamon-colored than the nominate subspecies. This subspecies is a division of C. b. affinis, but this distinction is not widely recognized. Purus means 'pure' or 'clean' in Latin.
- C. b. seri – found only on Tiburón Island in the Gulf of California. Its underparts are less cinnamon-colored than the nominate subspecies, and the spots on its abdomen are wider. A 2010 molecular genetics study found no difference between the genomes of C. b. seri and the mainland subspecies. The exact meaning of the subspecies name is unclear; it may be a corruption of sericeus, meaning 'silken' in Latin, or of the modern Latin serinus, meaning 'canary-yellow'.
- C. b. sandiegensis – found in Baja California and parts of southern California. This subspecies is not accepted by the American Ornithological Society, which instead believes it to be intermediate between C. b. couesi and C. b. bryanti, and classifies it as the former. However, it is accepted by the International Ornithologists Union. Its head lacks or has less of a red tinge compared to the nominate subspecies, and its eggs are darker than those of other subspecies. It is named for the city of San Diego.
Description
The cactus wren's coloration is brown with white speckles. The crown is chocolate-brown with a light red tinge. A distinctive white supercilium runs from the bill to the nape of its neck, which is brown with white markings. The chin is white, while the neck has black markings on a mostly white background. Their chest is white with brown or black speckles, and the belly is generally white with some brown or black streaks. The rump and back are gray to brown with white and black streaks. Both the lower underparts and the flanks are cinnamon-buff colored.
The cactus wren's ten primary and nine secondary flight feathers are barred, alternating between black and off-white. Its twelve rectrices are barred, alternating between brownish-black and pale gray-brown. The outer rectrices are white tipped. When flying, a white band can be seen on the underside of the tail feathers. The tail is barred in alternating stripes of black, white, and brown. The legs are brown to pink-brown.
Males and females look alike; juveniles can be distinguished by their paler coloration and red-brown to muddy-gray eyes. Adults have more red-brown to red eyes. Other distinctive features of juveniles include the lack of a white nape streak, and less noticeable black chest markings. Summer often takes a harsh toll on plumage; the intense desert sun and prickly vegetation fade and damage feathers. This wear and tear can make identification of juveniles more difficult. Worn feathers are replaced by molting, which happens in adults from July through October, usually in the bird's own territory. Not all feathers will molt in a single season.
Although the cactus wren looks similar to other wrens in its genus, cactus wren identification is made easier since the habitat of Campylorhynchus wrens does not overlap. A notable difference that can assist in identification of the cactus wren is the white tail band seen in flight. The spotted wren looks similar, but is paler and has fewer markings, and its habitat is in oak woodlands.