Cactus wren Information
Temporal range: 1–Present Ma
|Adult perched in a honey mesquite tree|
|Distribution map of the cactus wren.|
The cactus wren (Campylorhynchus brunneicapillus) is a species of wren that is endemic to parts of the southwestern United States, as well as northern and central Mexico. There are eight generally recognized subspecies, and the nominate species has a brown crown, with notable white eyebrows that stretch to the nape of the neck. The wings and feathers are brown, but are marked with black and white spots. The tail, as well as certain flight feathers, are also alternatively barred in black and white. The chest is whiter, while the underparts are cinnamon-buff colored. Its song is harsh and raspy and has been described by ornithologists like a car engine that will not start.
They are well-adapted to their native desert environment, and can fulfill almost all of their water needs from their diet, which consists of mainly insects supplemented with some plant matter. They are ground feeders and spend much of their time hopping on the ground for food. Cactus wrens are somewhat poor fliers and generally fly only to reach calling perches.
This wren's common name comes from its frequent use of saguaro and cholla cacti as nesting sites, which provide protection to both young and roosting adults. Their gridiron football-shaped nests are constructed first of plant material, then lined with feathers. Cactus wrens are non-migratory, and carve out and defend territories around their nests. Pairs are monogamous, with females incubating eggs while males build additional nests; both parents feed chicks.
Populations have been in decline as the species faces threats related to human activities and habitat loss. Habitat fragmentation and fire have been of particular concern, as the cactus wren is slow to disperse into new habitat. Introduced species, such as exotic grasses and domestic cats, have also hurt populations. Despite these threats, the cactus wren has proved adaptable and its population numbers in the millions – leading the International Union for Conservation of Nature to consider the cactus wren as 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 represents the largest wren in the US, 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 Blackwell-Rago et al. 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 also be unlikely, as the cactus wren was shown to be ancestral to the other species. Evolutionary study of the cactus wren suggests that it evolved in central Mexico about 1 million years ago, and that the wren then quickly spread to its modern range.   
The first cactus wren was described in 1835 by Frédéric de Lafresnaye. Lafresnaye was a Frenchman who never visited America; he procured his specimen from a naval officer who had recently returned from California. Lafresnaye thought that the specimen – which he called Picolaptes brunneicapillus – might have come from Peru (far outside the range of the wren), as the sailor 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, and as late as 1898. Subspecies were also incorrectly described as independent species. Matters were not helped by John Gould, who described the cactus wren – as Thryothorus guttatus – independently in 1836 and also failed to say where precisely his specimen had come from. Lafresnaye renamed Gould's find as Campylorhynchus guttatus in 1846, still not realizing that they had described the same bird. Although 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 through 1945, when it was determined that they were in fact different subspecies of the same bird. The cactus wren was placed in the genus Helodytes by the American Ornithological Union in 1894, but they placed it back in Campylorhynchus in 1947. :212-215
The genus name of the cactus wren is Greek, and roughly translates to "curved beak". The specific epithet translates as "brown hair", referring to the brown head and back. 
The 2007 study by Blackwell-Rago et al. established, using a molecular clock, 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 to eight are generally recognized.   Ornithologists Anders Anderson and Anne Anderson, in their compendium of 40 years of cactus wren research published in 1973, recognize only seven subspecies and do not classify C. b. sandiegensis as an independent subspecies. :211 The exact taxonomy of the cactus wren remains under debate, and not all subspecies are universally recognized. 
- C. b. brunneicapillus (Lafresnaye, 1835) – The nominate subspecies. Its range is in northern Mexico in Sonora and Sinaloa state. Its distinction from other subspecies is enhanced by its pure white chin. 
- C. b. guttatus (Gould, 1836) – Found in central and southern Mexico. It is duller and more grey than the nominate subspecies; its upper parts have less noticeable white markings.  Guttatus is Latin and means "speckled". :182
- C. b. affinis (Xántus, 1860) – Found in southern Baja California. Its underparts are paler, and it has less black marks than the nominate subspecies. Its rectrices, excluding the middle pair, have white bars. C. b. affinis tends to lay less eggs than other subspecies, generally two at a time instead of the more typical clutch of three to five, and those eggs are notably paler than that of other subspecies. This subspecies is sometimes further broken into C. b. affinis and C. b. purus, but this distinction is not widely recognized.  Affinis is Latin and means "allied" or "related". :182
- C. b. couesi (Sharpe, 1882) – Covers most of the cactus wren's range in the southern United States, including Nevada, Utah, Arizona, New Mexico, and Texas, as well as Sonora and Chihuahua states in Mexico. The American Ornithologists Union classifies all California 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. :120
- C. b. bryanti (Anthony, 1894) – Found along the western coast of Baja California, it is separated from the range of C. b. couesi by at least 150 mi (240 km).  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, (1861–1905). :79
- C. b. purus (van Rossem, 1930) – 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.  Purus is Latin and means "pure" or "clean". :325
- C. b. seri (van Rossem, 1932) – Found in the Gulf of California. Underparts are less cinnamon than the nominate, and the spots on its abdomen are wider.  The exact meaning of the subspecies name is unclear, it may a corruption of Latin sericeus, meaning "silken", or of modern Latin serinus, meaning "canary-yellow". :79
- C. b. sandiegensis (Rea, 1986) – Found in Baja California and parts of southern California. This subspecies is not accepted by the American Ornithologists union, which instead believes it to be an intermediate between C. b. couesi and C. b. bryanti, and classifies it as the former.  Its crown lacks or has lessened red tinge the on crown compared to the nominate subspecies. Its eggs are darker than those of other subspecies.  It is named for the city of San Diego. 
The cactus wren is the largest wren in the United States. This wren is between 18 cm (7.1 in) and 19 cm (7.5 in) long, and weighs in at between 33.4 g (1.18 oz) and 46.9 g (1.65 oz),  with an average of 38.9 g (1.37 oz). :207 It has a thick, heavy bill that is dull black, slightly curved downwards, and about the same length as the head.    :1 The tail is long and rounded. :207
The coloration of the nominate subspecies is brown with white speckles, and has distinctive white eyebrows that run from the bill to the nape of its neck.  The nape is brown, with additional white markings. The chin is white, while the neck has black markings on a mostly white background. The lower mandible is grayish and pale. The rump and back are grey to brown with white and black streaks. The chest is white with brown or black speckles. Its belly is generally white, with some brown or black streaks. Both the lower underparts and flank are cinnamon-buff colored. The crown is chocolate-brown with a light red tinge. 
The supercilium (stripe above the eye) is white. The cactus wren's 10 primary and 9 secondary feathers are barred, alternating between black and off-white. Its 12 rectrices (tail flight feathers) are barred, alternating between brownish-black and pale grey-brown. Outer rectrices are white tipped.   The tail is barred in alternating stripes of black, white, and brown.  Legs are brown to pink-brown. 
Males and females look alike; juveniles can be distinguished by their paler coloration and red-brown to muddy-grey eyes.  Adults have more red-brown  to red eyes.  Additional juvenile differences 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 moulting, which happens in adults July through October – usually in the bird's own territory – but not all feathers will be moulted in a season. 
Although it looks similar to other wrens in its genus, their identification is eased in that their habitat 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 less markings, and its habitat is in oak woodlands (where cactus wrens do not usually live). 
The main call of the cactus wren is a harsh and raspy series of “jar-jar-jar”,  or "char" notes, which increase in volume and pitch as the song goes on. Each part of the call lasts around 4 seconds, with 4–8 seconds between calls; calls can carry up to 1,000 feet (300 m). Cornell ornithologists described it as sounding "like a car that just won’t start". Males are the primary singers, although females can sing too – their song is weaker and higher pitched.  Males begin singing before dawn and prefer to vocalize from high vantage points, such as trees, telephone polls, tall cacti, or roofs. At least eight other songs exist besides the main call. A "buzz" or "tek" is given as a warning call. "Growls" serve as a mating and identification call. "Rack" calls are used for locating an existing mate, or other wrens – this call is often the first vocalization made upon leaving the nest. A high pitched "squeal" is given only during nest building, and is heard very rarely. "Scri" notes are let out during territorial disputes with other wrens. Chicks make various begging vocalizations, including a soft "peep". A "dzip" call is known to be made exclusively by fledglings. The main call is made while the beak is held just slightly above horizontal, and makes the feathers on the bird's throat noticeably extend from their normal position and vibrate.  :32
The cactus wren is a bird of arid and semi-desert regions. Its range includes the Sonoran and Chihuahuan Deserts, and generally requires spiny cactus to nest in. The cactus wren is not migratory,  and carves out permanent territories which it defends vigorously. Territories average 1.3 ha (0.013 km2) to 1.9 ha (0.019 km2).  The size and shape of territories change very little throughout the season. :18 Territory is defended from other birds by fluffing tails and feathers and vocal scolding. Persistent trespassers may cause the wrens to give chase. 
The cactus wren's range is bi-national, existing in only the United States and Mexico. In the U.S. it is present in California, Nevada, Utah, Arizona, New Mexico, and Texas. In California it is found mainly as southern coastal populations existing below 600 m (2,000 ft), but some have been found up to 950 m (3,120 ft). California populations have become increasingly fragmented due to habitat destruction. Nevada represents the northernmost portion of their range, they exist in the southern tip of the state, the most northern breeding population is found in Nye County, near Tonopah. They are found only in the smallest portion of southwestern Utah. Their range in Arizona is widespread throughout the southern part of the state, and along the Colorado river.  In Arizona it is found from sea-level up to 1,400 m (4,600 ft).  Populations in New Mexico exist in the south, down to along the Rio Grande and into Mexico. Their range in both New Mexico and Texas may be expanding northward. Texas cactus wrens live between sea-level and 1,800 m (5,900 ft), throughout the Texas panhandle, central Texas, and as far east as Travis County. In Mexico it is found in Sinaloa, Sonora, Chihuahua, Coahuila, Neuvo Leon, Hidalgo, and throughout Baja California.  On the Central Mexican plateau and in New Mexico it is found up to 2,000 m (6,600 ft).  Populations may be expanding their range in Baja California, but they are not found in the mountains or interior of Baja. 
The cactus wren forms permanent pair bonds, and the pairs defend a territory where they live permanently and year-round.  There is a distinctive greeting call between pair members, where they spread their wings and tails and give a harsh call.  The same motions are used as a breeding display, but with a non-ritualized duet call.  Since males and females are identical, birds recognize members of the opposite sex not by size or color but by behavioral differences. Males are more aggressive and are more frequent singers. :34 Mating displays begin with a growl-like noise, and end in gentle pecking.  Displays are incredibly short, lasting only two to three seconds. :35 Mating begins in late February and runs through March.  Egg laying begins around the same time, but is delayed at higher elevations.  Good monsoon conditions can extend breeding: young have been recorded in nests as late as August. 
Nests are built in cacti (notably cholla, prickly pear, and saguaro), thorny desert trees, or yucca.  Where available, jumping cholla is overwhelmingly preferred.  :22 Nests average about 3 ft (0.91 m) off the ground,  and are usually less than 10 ft (3.0 m) off the ground, but have been recorded as high as 30 ft (9.1 m). Nests are the size and shape of a gridiron football and are pouchlike in nature. The exterior is constructed of grass, twigs, feathers, weeds and other light detritus, while it is lined with feathers and down – which may come from cactus wrens or other species.   Nests built in urban settings use a much wider variety of materials, including many human made items such as paper, string, lint, and notably: chicken feathers, used as nest lining in great quantities where available. :24 Urban materials, while easily available, make for weaker and less sturdy nests. :28 A tube like entrance, about 15 cm (5.9 in) long, leads to the main nest cavity.  The entrance is often oriented to take advantage of the cooling effects of prevailing winds.  Nest building takes between one and six days, with Anderson and Anderson reporting an average time of 2.7 days. :26 The nesting pair generally focuses on nest building only in the first three hours of every morning. 
Multiple nests are often built. The first nest of a season may use an existing nest that has been renovated, although subsequent nests will usually be made from scratch. Adult roosting nests are usually separate from breeding nests, and are less sturdily constructed.  While the female lays one clutch, the male will start to build a second nest. As soon as the first brood fledges the female will assist in additional nest building. Once completed a new brood will be laid.  As many as three broods may be raised in a single year,   although one to two are more typical.  Up to 6 broods may be attempted in a year, but rarely more than two or three will survive. 
Cactus wrens lay three to four (although as many as seven have been recorded) white to pale pink eggs  covered in brown speckles, which are smooth and ovate. Eggs are 23.5 mm (0.93 in) × 17 mm (0.67 in) and average 3.57 g (0.126 oz) in weight. Egg laying begins about a week after nest completion, and is done one egg per day in the morning. Incubation takes about 16 days and is done solely by females. Wrens are known to destroy the eggs and nests of other nearby birds, but do not engage in, nor suffer from, brood parasitism.  
Young are born asynchronously with their eyes closed, and are mostly bald, with sparse patches of fuzzy white down.   They are fed (mostly insects) by both parents. Young make begging vocalizations at least as early as two days old, with the vocalizations evolving as the chicks age.  Chicks are dependent on their parents for the first three weeks after hatching. Nestlings open their eyes between six and eight days, and grow feathers starting at 8 days post hatching (although quills emerge as early as two days after hatching).  Adult feather length is reached by 20 days old.  Nestlings reach adult weight at about 38 days, and gain independence between 30 and 50 days post-hatching.  The young can stay in the parent's territory for a while after fledging,  but will be driven off by the next breeding season. Juveniles that stay around can help take care of successive broods. 
The cactus wren primarily eats insects, including ants, beetles, grasshoppers, termites, and wasps.  The cactus wren will also take seeds, fruits, nectar, and even small reptiles. Foraging begins late in the morning and is versatile; the cactus wren will search under leaves and ground litter and overturn objects in search of insects, as well as feeding in the foliage and branches of larger vegetation.  Some individuals have even learned to take insects caught in vehicle radiator grills.  Increasing temperatures cause a shift in foraging behavior to shady and cooler micro-climates, and activity slows during hot afternoon temperatures.  This is partly to conserve water and keep cool during hot days, but also because their insect prey is more sluggish and thus easier to catch in cool temperatures.  Almost all water is obtained from food, and free-standing water is rarely used even when found.  The cactus wren can survive as a true xerophile, existing without any free water. Eating cactus fruits is an important source of water, and individuals have even been seen drinking cactus sap from wounds inflicted by Gila woodpeckers.  Cactus wrens also sip nectar from saguaro blossoms and eat insects trapped within, serving as pollinators in the process. :187
Parents feed young with whole insects, although they may first remove wings or legs. One study found that the average caloric needs of a developing chick required about 15 medium sized grasshoppers per day.  Cactus wrens generally feed and live in pairs,  or in family groups from late spring through winter.  Flocks of cactus wrens are reported to form, but seem to do so only extremely rarely. Flocking has only been observed in areas of abundant forage, and does not last longer than a few hours. :18-19 As ground feeders they spend much of their time on the ground and are not exceptionally strong fliers, with any flights being somewhat erratic – switching between rapid wing flapping and gliding. 
Nests built in cactus provide a degree of protection to young, yet even in cactus, young wrens are vulnerable to predation by coachwhip snakes.  When threatened, young in nests were observed to try to blend in with the nest, and flattened themselves against the nest walls.  Adults are preyed upon by coyotes, foxes, hawks, bald eagles, domestic cats, and greater roadrunners.    Upon detection of predators, cactus wrens will usually mob the predator and vocally scold it.  They may also chase ground based predators and intruders.  Predator alarm calls are usually a low buzz, or sometimes a staccato "tek" which is repeated.  In response to birds of prey adults may attempt to move closer to the ground or leave calling spots. 
Cactus wrens can live at least 5 years in the wild, :152 but average lifespan is two years for males, and 1.3 years in females.  Year-over-year decline is high, often a result of predation. Roughly one third of clutches laid each year are lost. Fledglings are most vulnerable to predation, and adult wrens may occasionally fail to lead all fledglings back to roosting spots. Fledglings left outside of roosts overnight face greatly increased predation. The main cause of death in young seems to starvation due to lack of foraging experience. :195
Cactus wrens share a very similar range to the curve-billed thrasher, as well as a favorite species to nest in: the jumping cholla. Because of this, interspecific conflict is frequent. Fights over food are rare, but fights to protect fledglings are heated. They will vigorously work to destroy each other's nests, although typically only roosting nests, not breeding nests, are destroyed. Despite this, nests of curve-billeds and cactus wrens may still be concurrently and successfully raised even feet away from each other. Ornithologists Anderson & Anderson noted a minimum nest distance of a highly unusual 6 inches (15 cm) (neither nest was destroyed by the either throughout the entire season), although average interspecies nest distances were well over 100 feet (30 m). Nest destruction is almost always unsuccessful, and less intense, during breeding times, as both species adamantly defend their own nests. Once breeding season wanes, and fledglings emerge, competition becomes more fierce. :168-187
The cactus wren is the state bird of Arizona. It was designated as such on March 16 of 1931, by the Arizona State Legislature, as House Bill 128.   The bill refers to the bird as both the "Cactus Wren" and "Coues' Cactus Wren". The State Legislature specifically designated subspecies C. b. couesi as the state bird. :1 The subspecies namesake, Dr. Coues, served as a surgeon at Fort Whipple in Arizona from 1864 until at least 1871, and again in 1880, and was involved in naturalistic surveys of the then territory. 
The cactus wren is abundant in most of its native range, although its numbers may be declining in Texas and southern California.  The IUCN classifies its population as "decreasing", but ranks the species conservation status as Least Concern.  Current population estimates put the species at about seven million individuals, with slightly more than half residing in Mexico, and the rest in the United states. Populations declined 55% between 1966 and 2015,  but decline is not consistent across the range. U.S. populations have decreased more than Mexican ones, but in some local populations – such as in Nevada, New Mexico, and the Chihuahuan desert – populations have actually increased. Populations in Texas have faced the steepest declines, followed by Arizona and California. 
Coastal populations in southern California face threats due to habitat loss as a result of suburban development. Populations have been highly fragmented due to urbanization, which may lead to genetic differentiation among isolated populations and could threaten overall species viability. Similar species which nest in coastal sage scrub (the preferred nesting habitat of coastal cactus wrens) have faced high levels of extinction.  California subspecies C. b. sandiegensis was petitioned to be listed as federally endangered in 1990, but was not due to taxonomic disputes as to whether C. b. sandiegensis was actually distinct from the rest of the cactus wren population. C. b. sandiegensis is however listed as a "California Species of Special Concern." 
Across the cactus wren's range, habitat fragmentation is a major problem. Urban populations have faced especially steep declines. Habitat degradation at the edge of the habitat/urban interface led to general population loss. Study showed that fire had an outsized impact on cactus wrens due to their territoriality, with populations persisting only in unburned pockets. These issues are compounded by the apparently poor ability of the cactus wren to disperse: each subsequent generation of wrens will usually not travel great distances to establish territory. Most young, once chased out of their parents territory, will generally establish their new territory directly adjacent to their parents. Other issues include invasive grasses, which take up valuable foraging space, as the wren only forages in mostly open areas. Domestic cats also take a high proportion of birds in urban settings.  Despite the threats it faces, the cactus wren has proved adaptable, especially to human modifications. It can survive in degraded habitat, as long as suitable nesting habitat, such as spiny cactus, remain. 
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