Wrens

(Troglodytidae)

Class Aves

Order Passeriformes

Suborder Passeri (Oscines)

Family Troglodytidae

Thumbnail description
Very small to medium-sized passerines, plumage usually predominantly brown, sometimes with striking black or white markings; frequently with superbly beautiful songs that are often the product of both sexes singing in concert

Size
3.6–8.8 in (9–22 cm); 0.26–2.25 oz (7.3–62.8 g)

Number of genera, species
14 genera; 60 species

Habitat
Forests, scrubland, suburban areas, marshes, grassland, rocky areas

Conservation status
Critical: 1 species; Endangered: 2 species; Vulnerable: 3 species; Near Threatened: 3 species

Distribution
North and South America, except for northern Canada, Alaska, and most of the West Indies; one species in Europe, North Africa, Middle East, central Asia to Japan, eastern Siberia, and Taiwan

Evolution and systematics

The classification of the wren family has long been an area of dispute among scientists. The commonly held view over much of the twentieth century was that wrens were very closely related to dippers and more distantly related to mockingbirds and thrushes. Given the obvious physical similarities between wrens and dippers—the stumpy shape, usually short tail, and rounded wings—as well as the fact that both groups build domed nests with a side entrance-hole, this seemed eminently reasonable. However, more recent work based on DNA studies has radically changed this picture. Wrens appear to be most closely allied to the New World gnatcatchers and gnatwrens, and rather more distantly to the creepers (treecreepers) and nuthatches; dippers, by contrast, are evolutionarily closer to thrushes than to wrens.

The ancestral seat of the wrens is in the New World, but precisely where is a source of debate. At the time when most present-day passerine families were evolving, there was no continuous land bridge between North and South America. One theory postulates an ancestral center somewhere in present southwestern North America, followed by the invasion of South America. This viewpoint is by no means universally held, and an origin in northern South America has some advocates. The fossil record of wrens is extremely scanty and so recent as to be of little help in elucidating the geographic origins of the family. The greatest abundance of modern wrens is in southern Central America and northwestern South America.

The precise number of species of wrens is a fluid and debatable quantity. Although only four totally new species have been described to science since 1945 (the most recent in 1985), different authorities have wildly differing opinions as to the taxonomy of the family. Thus the house wren group, occupying the Americas from Canada to Tierra del Fuego, has been variously treated as one species or as many as ten. Peters checklist contains 60 species in 14 genera; more recently, Clements has 78 species in 16 genera, while the most recent studies suggests 83 species in 16 genera. Wren taxonomy is currently in a state of great flux, and both the total number of species and their allocation into genera will almost certainly change in the near future. The bizarre and aberrant Donacobius, a raucous and rambunctious inhabitant of South American marshes, is sometimes classified as a wren, a viewpoint that varies among taxonomies.

Physical characteristics

In size, wrens are among the smaller birds. In North America, the only lighter birds are the kinglets, hummingbirds, some smaller warblers, and the gnatcatchers. The largest wrens are about the same size and weight as a small thrush, and the majority weigh less than a house sparrow. Plumage is generally brown, buff, or gray-brown, usually with prominent barring on wings and tail. Some of the tropical species, especially of the genus Thryothorus, have bright reddish brown plumage, frequently with attractive and striking patterns of black and white on the face and underparts. A few terrestrial South American species have bare blue skin around the eye.

Wrens spend most of their time foraging in thick vegetation and consequently tend to have short, rounded wings, more suited to brief flights between adjacent thickets than to sustained flight. However, several short-winged species—such as the winter, house, and sedge wrens—are long-distance migrants, undertaking migrations of 600–1,200 mi (1,000–2,000 km) in some cases. Migration occurs after dark. Many wrens have short, stumpy tails (usually with 12 feathers) that are frequently carried cocked up over the back, although the unusual Odontorchilus (tooth-billed wrens) of South America are long-tailed gnatcatcher-like birds.

Wrens are largely insectivorous birds, and their bills reflect this diet. The bills are long and fine, never heavy or conical. Within the family there is substantial variation in feeding specialties with corresponding variation in the bill. For example, the "cactus" wrens of the genus Campylorhynchus, species that make their livings by probing into epiphytes, tend to have finer bills than arid-country species, which take coarser prey. The cliff-face and rock specialists of the genus Hylorchilus have exceptionally long and fine bills to aid in probing narrow crannies among rocks.

The plumage of the sexes is always very similar in wrens. Juvenal plumage may, in some cases, be substantially different from that of adults, but in other cases, very similar.

Distribution

The wrens are an American family. With the notable exception of the winter or northern wren, they are confined entirely to the Nearctic and Neotropical zoogeographic regions. Within this vast area, ranging from 62° north in Alaska to 55° south in Tierra del Fuego, the abundance of wren species varies greatly, with the maximum diversity in southern Central and South America. Canada, with an area of 3.85 million sq mi (10 million km²), has eight species; the United States (3.8 million sq mi, 9.8 million km²) has ten; Mexico (760,000 square miles, 1.98 million km²) has 35, with 11 species that are endemic; Panama (30,000 sq mi, 77,700 km²) has 21; and Colombia (440,000 sq mi, 1.14 million km²) has 30. Species abundance remains high in the Andean chain, but drops off sharply in the lowlands of the Amazonian basin.

The high diversity in the mountainous regions of Central and South America is at least partially the result of the varied terrain; frequently several species are found in close proximity in the different habitats created by different altitudes and the varying precipitation levels caused by mountains and rain shadows. Conversely, the Amazonian basin is of almost uniform altitude. Furthermore, in lowland areas the families of the antbirds and ovenbirds reach their maximum abundance, doubtless competing for food resources with wrens. In South America south of Bolivia, the number of species diminishes rapidly, with essentially only two species south of the tropic of Capricorn.

Curiously, wrens are almost absent from the Caribbean subregion; the southern house wren extends to some of the Windward Islands and the peculiar and unique Zapata wren (Ferminia cerverai) occupies a few square miles of swampland in Cuba, but much apparently excellent habitat on the large islands is inexplicably wrenless.

One species, known in North America as the winter wren (Troglodytes trogodytes) but in Britain simply as the wren, crossed the Bering Strait into the Old World. Lacking competition, it has expanded across three further continents, from Kamchatka and Taiwan in the east to Morocco and Iceland in the west, occupying a diverse range of habitats, from remote sea-girt islands to Himalayan scrubland and suburban gardens.

The different genera of wrens have different centers of abundance. By far the most widespread genus is Troglodytes. It is both the northernmost and the southernmost genus in the Americas, and the only one in the Old World. It includes a modest number of species, some of which have very restricted distributions in the mountains of Costa Rica, Panama, and Colombia. The genus Thryothorus, at 21 species, is by far the largest, and has an almost exclusively tropical distribution. The genera Salpinctes, Catherpes and Hylorchilus, comprising rock, canyon, and alllied wrens, occur from western Canada to Costa Rica and specialize in living in rocky habitats and cliff-faces. From Arizona to Ecuador and Brazil are found the largest wrens, the rambunctious and boisterous members of the genusCampylorhynchus, which includes the familiar cactus wren (Campylorhynchus brunneicapittus) of the arid American southwest as well as several highly restricted species found in limited areas of Mexico. In the thick tropical forests from Mexico to Brazil and Bolivia is found the genus Henicorhina, which includes two widely distributed species, one highland and one lowland, as well as one that was only recently discovered in a few mountains in Peru and Ecuador. The genus Microcerculus is a specialist of dense tropical forest, usually at low elevations, and occurs in these habitats from Mexico to Brazil and Ecuador. In Andean South America the genus Cinnycerthia is found exclusively in wet mountain forest, often at considerable elevations, while the genus Cyphorhinus is found at lower elevations from Honduras to Bolivia and the Guianas. The distribution of the four species of the marsh-specializing genus Cistothorus is peculiar. Two are found in restricted areas of Venezuela and Colombia. One occurs across the whole of North America, from California to Florida and New Brunswick. The fourth, the sedge wren (Cistothorus platensis), is found discontinuously from the Canadian prairies through Central and South America to Cape Horn and the Falkland Islands. The other wren genera are almost all confined to the New World tropics, with the exception of Bewick's wren (Thryomanes bewickii), which occurs across western and central North America.

Habitat

Wrens have evolved to take advantage of virtually all types of habitat in their geographic range. However, certain genera tend to specialize in particular kinds of habitat. The genus Cistothorus, the marsh wrens, is predominantly found in marsh-edge vegetation such as reeds and cattails, though one species also occurs in wet high-altitude Andean grassland. The most arid areas are occupied by the large wrens of the genus Campylorhynchus, though again, some members occur in lowland tropical forest. The largest genus is Thryothorus, the majority of whose species live in dense forest or forest-edge, often at considerable elevations. Some wrens have become very specialized; the canyon wren of western North America is essentially confined to canyons, more rarely sea-cliffs. The two members of the genus Hylorchilus occur exclusively in tall forest on limestone karst outcrops. The majority of species in the tropics are found in forest. The highly terrestrial members of the genus Microcerculus are found in wet lowland forest, and the genus Cinnycerthia occurs in wet montane forest. Wrens do not usually adapt well to gross habitat modification, but a few species have developed a reasonable coexistence with humans. Northern and southern house wrens are abundant in abandoned farmland, clearings, and well-treed suburbs, and undoubtedly have expanded their range to take advantage of forest clearing. The Bewick's wren expanded greatly into eastern North America as agriculture moved westward in the nineteenth century. The winter or Eurasian wren occupies a range of habitats. In North America, it tends to be restricted to cold, wet northern forest. However, after it crossed the Bering Strait into three new continents, it was without competition from any other wrens, and it expanded into a great variety of habitats, from low brush in remote oceanic islands to high-altitude bushland in Central Asia, cedar forest in North Africa, and suburban gardens in England.

Behavior

Wrens tend to be a retiring and secretive family. This is by no means universal—the large cactus wrens of the genus Campylorhynchus are noisy, uninhibited, and conspicuous—but most wrens tend to spend most of their time in the lower levels of dense vegetation, going about their daily lives with an immense busyness, but liable to disappear from view at the slightest disturbance. This is especially true of the nightingale wren (Microcerculus marginatus), which is legendarily difficult to observe. Wrens are almost always first detected by song. Wren vocalizations are loud beyond all proportion to the size of the bird; some tropical wrens are stated to have a vocal production ten times louder, weight for weight, than the crowing of a cockerel. Indeed, the name for the house wren in the Ojibwa language of western Ontario means "he who makes a lot of noise for his size." Many species of tropical wrens, especially in the genera Campylorhynchus and Thryothorus, have developed elaborate, mutual songs by both sexes. In some cases these are duets, with both birds singing simultaneously. More often, though, they are antiphonal, with each sex singing a different part. The contributions often are so tightly interwoven that the casual observer would not guess that more than one bird was involved.

Another peculiar fact of wren behavior, widely spread among several genera, is the destruction of eggs of other birds, sometimes of their own species, but frequently of others. In the marshland communities of Canada and the United States, the marsh wren (Cistothorus palustris) may destroy enough eggs of the much larger red-winged and yellow-headed blackbirds as to have a significant effect on their breeding success. Marsh wrens can, in fact, be caught in traps baited with small eggs.

The decline of the Bewick's wren in eastern North America has been correlated to the increase in the population of the house wren (aided, ironically, by the provision of nest-boxes). Two closely related Campylorhynchus wrens, the giant wren of southern Mexico and the bicolored wren of northern South America have the local name Chupahuevo, literally, egg-sucker, acquired apparently by their depredations in hen houses. The function of egg predation is not clear; it may reduce competition on the nesting-ground. Sometimes destroyed eggs are eaten, but frequently they are simply punctured and left.

Feeding ecology and diet

Surprisingly little is known about the feeding ecology of many—in fact the majority—of wren species. The 10 North American species are well-studied, but for many tropical species the only information available comes from collectors' notes on the labels of museum specimens, which are often more cryptic than enlightening. Generally speaking, almost all species eat largely or wholly an arthropod diet. The large wrens of the genus Campylorhynchus are something of an exception, since they do take substantial quantities of vegetable matter, such as cactus seeds. In some instances small frogs or, in the case of the Zapata wren, substantial lizards may be taken. Egg-destruction occurs in a variety of species, but eggs so attacked are not always eaten. Feeding techniques of wrens vary among different genera.

Food items are generally taken from a perched position, not caught in mid-air. Microcerculus feed almost exclusively among forest-floor litter; the wing-banded wren specializes in foraging in rotted logs. Most other wren species feed in the lower levels of tangled vegetation, but some species range higher up; the aberrant genus Odontorchilus is unusual for feeding mostly in the forest canopy. Some species of tropical wren will briefly join mixed flocks following ant-swarms, but no species is truly a habitual ant-follower. In Arizona, cactus wrens have learned to exploit a novel food source, the squashed and conveniently dehydrated insects on the radiators of parked cars.

Reproductive biology

There are three unusual features in the reproductive biology of some wren species: multiple nest building, polygamy, and cooperative nesting. The building of superfluous nests occurs in many genera of wrens, but is most pronounced in the marsh-living genus Cistothorus. Male marsh wrens may build up to 20 nests in a season. Typically, nest construction is by the male, with the female apparently selecting the nest to be used for breeding and adding the lining. The sheer amount of energy that goes into building apparently surplus and useless nests suggests that it has a strong evolutionary advantage, but there is debate as to the actual nature of that advantage. Doubtless it is useful to have back-up nests that can be rapidly refurbished in the event of damage to the breeding nest, but after one or two back-ups that advantage must surely be played out. It has also been suggested that extra nests act as decoys to predators, or that the number of nests that a male makes is an indication of his reproductive vigor; indeed, if their surplus nests are experimentally removed, male marsh wrens have difficulty attracting mates. Surplus nests are also useful for roosting and may be constructed exclusively for that purpose. In the white-breasted wood wren, breeding nests are substantial and well concealed. Nests specifically built for roosting tend to be flimsy, situated higher up, and have less camouflage, since the ability to make a rapid exit on disturbance is apparently of more importance.

Most wren nests are domed structures with a side entrance, although nests built by some cavity-nesting species such as the northern house wren have no roof. In many species—for example in the genera Thryothorus and Uropsila—the nest is an elaborate, often a two-chambered, beautifully built structure; in others, for example, the song wren (Cyphorhinus aradus), it is tattered and untidy. Sometimes, as in the winter wren, nests are artfully concealed. By contrast, the cactus wren usually builds in savagely spiny cholla cacti with little effort at concealment. Many tropical wrens specifically nest in acacia trees that harbor aggressive colonies of symbiotic ants that attack any intruder, and the birds gain vicarious protection from predators such as monkeys. In the absence of such ants, some wren species deliberately site their nests next to pendant hornets' nests for the same purpose.

Clutch size in wrens varies from two in many tropical species to up to ten in temperate zones. Eggs are white, immaculate to heavily speckled, or rarely, blue. Incubation is by females alone, but young are fed by both sexes, except in polygamous species, where male help may be rare.

Polygamy is especially pronounced in the genus Cistothorus, reaching its peak with the marsh wren. In some populations of that species, more than half of the breeding males are bigamists, and a significant number are trigamists. The sex ratio among marsh wrens also seems to be skewed, with females outnumbering males almost two to one.

Cooperative breeding occurs in a number of species, but reaches its greatest development in the stripe-backed wren (Campylorhynchus nuchalis) of northern South America. There, groups of up to 14 birds will defend a territory, but only one dominant pair actually breeds. Nesting success and the rearing of two broods a year are both strongly correlated to group size; without at least two helpers a pair will not attempt a second brood. Birds in a group are usually blood relations, but after a year or so all females and some males disperse to other groups, thus minimizing incest.

Large gaps remain in human knowledge of wren breeding biology. For example, of the wrens found only south of the United States-Mexican border, the nest and eggs have never been described in about a third of species, and for a good many others available information is sparse.

Conservation status

Most of the 60 species of wren are in no immediate danger of extinction, though with forest destruction the ranges of many have been fragmented and the total population doubtless substantially reduced. In some instances human activity has helped wren populations, notably in the case of the northern and southern house wrens, which do not occur in undisturbed thick woodland but readily take to second growth and bushland, the amount of which greatly increased as European settlement spread across the Americas. Bewick's wren expanded eastward in the nineteenth century for the same reason, but may now be retreating due to competition and egg destruction by the northern house wren.

There are several species of wren for which there is cause for concern. The unique Zapata wren of southwestern Cuba inhabits a very small area at a rather low density. Discovered in 1926, it was feared extinct in the 1970s but appears to have a current population of about 75–100 pairs. The main threats are the burning of its marshland habitat and predation by introduced mongooses. Its current status is Endangered. Nice-foro's wren (Thryothorus nicefori) was discovered in a tiny area of Colombia in 1945 and not seen again until 1989. The population is obviously quite small, and the habitat currently unprotected and at risk; Niceforo's wren was classified as critically Endangered in 2001. Apolinar's wren (Cistothorus apolinari), which is Endangered, also occurs in a very restricted range in Colombia. It has very specific habitat requirements, namely lakeside reed-beds, and much of the habitat lies in well-populated areas; several previously known areas are now lost. The two species of the genus Hylorchilus each occupy very specific and restricted habitat in southern Mexico, being tied to open forest on karst limestone outcrops. Sumichrast's wren (H. sumichrasti) has an overall range of about 2,000 sq mi (5,200 km²), but only occurs in small isolated pockets in that area; Nava's wren (H. navai) occurs in isolated pockets in an even smaller overall range. Some of the range of Nava's wren is protected, but none of that of Sumichrast's wren; they were classified in 2001 as Vulnerable and Near Threatened, respectively.

Although no full species of wren have been lost, several island races have become extinct in recent times. Thus two races of Bewick's wren, formerly found on islands off the Californias, are gone, as is the Martinique race of the southern house wren. Two other West Indian races of the same species, on St. Lucia and Guadeloupe, are in very parlous states; and finally, an isolated race of the rock wren on San Benedicto in the Revellagigedo islands off western Mexico became extinct in a very spectacular manner in 1952, when its island home erupted catastrophically.

There are several other species or subspecies of wren found only in very small ranges: the Clarion (Troglodytes tanneri), Socorro (Thryomanes sissonii), and Cozumel wrens on the Mexican islands of the same names; the giant wren, occurring only in Chiapas state of Mexico; and the Yucatan wren (Campylorhynchus yucatanicus) in the Yucatán peninsula. Although the first two are classified as Near Threatened due to their small island range, most recent observers have found them to be fairly common. The other three species seem to be common to abundant in their limited ranges. One further South American species, the bar-winged wood wren (Henicorhina levcoptera), has a very limited distribution in Ecuador and Peru, where it is probably protected by the remoteness of its mountain habitat.

Significance to humans

Wrens have no economic impact on agriculture and probably little on forestry. Nevertheless, it is hardly surprising that birds so abundant and so vehement of song should figure as prominently in legend and folklore as wrens do. In Celtic mythology, the wren was the king of the oak tree and the symbol of the old year, while the robin was the symbol of the new year. This gave rise to a tradition of hunting the wren at the winter solstice to make way for the robin. On the Isle of Man and in southern Ireland, groups of boys caught wrens on St. Stephens Day (December 26), which were then paraded around with accompanying verse and solicitations for modest funds. "Wrenning" was not, in fact, confined to Celtic regions of the British Isles, but up until the nineteenth century was widespread over much of England as well. The verses chanted often made reference to the wren as the king of the birds, a belief widespread in the mythologies of very diverse peoples in Europe. In fact, in several European languages the name of the wren implies royalty—Winterkonig (Winter King) in Dutch and Zaunkönig (King of the Fencerow) in German, for example.

Although the origins are obscure, there is a common theme in cultures as various as Ojibwa and Scottish Gaelic of the wren attaining kingship by outwitting the eagle. In one wellknown story, all the birds agreed to decide their king by holding a competition to see who could fly highest. When the eagle, who had outflown all the other birds, could climb no more, the wren, which had concealed itself among the eagle's back feathers, popped out and flew just a little higher. The origin of this story may be an Aesop fable that has now been lost. In Native American folklore the wren appears frequently, often as a busybody; in Cherokee belief the wren is supposed to observe women in labor, rejoicing in the birth of a girl and lamenting the appearance of a boy.

Species accounts

List of Species

Cactus wren

Campylorhynchus brunneicapillus

taxonomy

Picocolaptes brunneicapillus Lafresnaye 1835, Guaymas, Mexico. Eight subspecies recognized.

other common names

French: Troglodyte des cactus; German: Kaktuszaunkönig; Spanish: Matraca Desértica.

physical characteristics

7.2–7.6 in (18–19 cm); 1.2–1.6 oz, mean 1.4 oz (33.4–46.9 g, mean 38.9 g). The largest species of wren in the United States. The bird is chocolate-brown above, with a plain cap. The back is heavily streaked with black and white, the wings prominently barred with buff and blackish, the tail feathers with alternating blackish brown and gray-brown bars, the outer tail feathers conspicuously barred black and white. Underparts are buff-white and heavily spotted with black, especially on chest. Lower flanks are buff. It has a conspicuous white supercilium. Eyes are reddish brown, bill dull black with paler base, legs pinkish brown. Sexes are similar. The juvenile has less well-defined streaks and spots; eye color is muddy gray-brown.

distribution

Resident from southeast California, southwest Nevada, sourthern Arizona and New Mexico, southwest Texas through central Mexico as far south as Michoacán and Hidalgo; Baja California.

habitat

Semi-desert from sea level to 4,500 ft (1,400 m), rarely to 6,500 ft (2,000 m), in various vegetation-types, provided that there are spiny cacti such as cholla for nesting. Will adapt to badly degraded habitat so long as some spiny cactus nesting sites remain.

behavior

A rambunctious and noisy bird, usually found in pairs or family parties. Song is a loud, harsh series of "jar-jar-jar" notes, frequently delivered from the top of a cactus or other perch. Roosts in nests that are often built for that purpose; old birds may roost alone, fledged broods are usually together.

feeding ecology and diet

Majority of food is invertebrate (ants, wasps, spiders, caterpillars, etc.); also eats small frogs and lizards. Vegetable matter includes cactus seeds and fruit; may visit bird feeders. Can exist without drinking, but will drink if water is available. Tends to feed on the ground, overturning litter and stones for prey.

reproductive biology

Monogamous. Nest is a conspicuous ovoid ball with a side entrance hole, made of dry grasses and fibers and lined with feathers. Nests are almost invariably located in spiny cacti; little effort is made at concealment. Eggs usually number three to five, sometimes two to seven, are buff or pinkish in color and finely speckled with reddish brown. Populations in Baja California tend to lay smaller clutches. Incubation is by the female alone, about 16 days in length. Young are fed by both sexes for 19–23 days. In Arizona, nesting may begin as early as January, more usually February. Multibrooded; may attempt up to six broods a year, but only three successful broods are reared. Unlike tropical members of its genus, additional birds (other than the breeding pair) rarely help at the nest.

conservation status

Not threatened. In suitable habitat one of the most abundant species. Can withstand significant habitat modification provided some spiny cactus remain for nesting sites.

significance to humans

A familiar and popular local species, it is the state bird of Arizona.

Canyon wren

Salpinctes mexicanus

taxonomy

Thryothorus mexicanus Swainson, 1829, Real del Monte, Hidalgo, Mexico.

other common names

French: Troglodyte des canons; German: Schluchtenzaunkönig; Spanish: Saltaparad Barranquero.

physical characteristics

5–5.6 in (12.5–14 cm). Male 0.35–0.52 oz (9.9–14.8 g), female 0.35–0.43 oz (9.9–12.2 g). A slender, long-tailed wren with a

fine decurved bill, quite unlike any other species in its range or habitat. Crown and nape are gray-brown, back is reddish, rump is chestnut. Throat and upper chest are white, contrasting with chestnut-brown belly and rich red-brown lower belly. Crown and back have numerous white speckles; wing and tail feathers have blackish transverse bars. Eyes are dark brown, bill is grayish black and paler at base, legs are dull gray-black. Sexes are similar. In the juvenile, pale speckles on upperparts are obscure, and underparts are less brightly colored.

distribution

Mountainous regions of western North America from southern British Columbia, east to Montana, Wyoming, South Dakota, and western Texas; south through Mexico to Oaxaca and disjunctly in Chiapas. Largely sedentary; northern populations descend in winter. Some vagrant records outside breeding range.

habitat

Confined to areas with rock faces, canyons, bluffs, and, rarely, sea-coasts; also occurs in ancient ruins, especially in Mexico. Sea-level to 9,800 ft (3,000 m), lower in northern parts of range.

behavior

Forages on rock faces, over which it crawls much in the manner of a wallcreeper; the tail is not used as a prop as in the true creepers. Frequently enters narrow crevices and cracks in rock face; will sometimes hawk for aerial prey, more rarely forages on ground. Song is a superb descending trill, ending in a series of six or seven beautiful clear notes.

feeding ecology and diet

Specially adapted to gain access to narrow cracks in rock; the long bill, flattened head, special articulation of the skull and spine, and widely spaced legs are all adapted for this purpose. Food is entirely invertebrate, including beetles, spiders, termites, etc. Has been seen to steal paralyzed spiders from nests of mud-dauber wasps.

reproductive biology

Monogamous. Nest, built by both sexes, is an open cup of hair, feathers, and wool with a base of twigs situated in crevices in rock faces; sometimes in artificial cavities in ruins or buildings. Eggs number three to seven, usually six; they are glossy white with fine reddish spots. Clutch size is smaller in Mexican populations. Incubation is by the female alone, for 12–18 days. Young are fed by both parents for 12–17 days. Does not build special roosting nests.

conservation status

Not threatened; the remoteness and ruggedness of its habitat gives it substantial protection.

significance to humans

None known.

Slender-billed wren

Hylorchilus sumichrasti

taxonomy

Catherpes sumichrasti Lawrence, 1871, Mato Bejuco, Veracruz, Mexico.

other common names

English: Sumichrast's wren; French: Troglodyte de Sumichrast; German: Schmalschnabel-Zaunkönig; Spanish; Saltaparad de Sumichrast.

physical characteristics

6–6.6 in (15–16.5 cm), 1.1 oz (29–30g). A bulky and dark-plumaged wren with a notably long and slender bill. Upper-parts including tail are a deep chocolate-brown. Wings are dull blackish brown. Throat is whitish brown, chest orange-brown,

belly rich chocolate-brown. Lower belly and flanks have small white spots. Eyes are brown; bill is very long, slender, and decurved, blackish with dull orange-yellow base; legs are dark gray. Sexes are identical. The juvenile has a dull buff throat with diffuse scaling and whitish flecks on the belly.

distribution

Restricted area in the Mexican states of Veracruz, Oaxaca, and Puebla; total area is about 2,300 mi² (6,000 km²), but actual range within this area is much less due to exacting habitat requirements.

habitat

Confined entirely to karst limestone country with large mature forest canopy.

behavior

Typically hops over boulders, tail cocked, bobbing like a dipper. Is not excessively wary, but rather curious. Generally occurs low to the ground, rarely at any height in vegetation, and most frequently on rocks and boulders. Normally found alone or in pairs. Both sexes sing in a distinguishable manner. Males have two song types: one an arresting series of loud clear notes, finishing with a longer series of slow, descending notes; the other is a song of shorter notes alternating in pitch. Female song is a single note repeated in a series.

feeding ecology and diet

Most often forages in mosses and lichens on boulders and rock faces, frequently disappearing into crevices. Food is almost entirely invertebrate.

reproductive biology

Little known; only three nests described, two in crevices in rocks and one in roof of limestone cave. Eggs are white, number three, and are laid in May. Incubation and fledging periods are unknown. Not known if the species is multiple-brooded, or whether polygamy or nest-helping occur.

conservation status

Near threatened. Highly restricted both in geographic range and in habitat. Does, however, seem to be able to tolerate some disturbance to habitat, such as the planting of coffee bushes, provided the disturbance is moderate. No part of its range is under formal protection.

significance to humans

None known.

Marsh wren

Cistothorus palustris

taxonomy

Certhia palustris Wilson, 1810, eastern Pennsylvania. 15 subspecies recognized.

other common names

English: Long-billed marsh wren; French: Troglodyte de marais; German: Sumpfzaunkönig; Spanish; Saltapared Pantañero.

physical characteristics

4.5–5 in (11.5–12.5 cm). Male 0.43–0.5 oz, mean 0.45 oz (12.1–14 g, mean 12.7 g). Populations in western North America weigh slightly less. Crown is blackish brown; back is

medium-brown with broad collar of blackish; streaked white on upper back. Wings and tail are reddish brown with darker bars. Supercilium is whitish, contrasting with cap and brown eye-stripe and ear-coverts. Underparts are gray, becoming buff on lower belly and flanks. Eyes are brown; bill is dark brown above and yellowish brown below; legs are pale brown. Sexes are identical. The juvenile rather duller than an adult with reduced white streaking on back; supercilium is less obvious.

distribution

Breeds across North America from New Brunswick and Virginia to British Columbia, north to northern Alberta, south to central Midwestern states and California; also coastal marshes along the eastern United States seaboard and Gulf of Mexico. Populations in eastern and western North America may be two distinct species.

habitat

Freshwater marshes with cattails, bulrushes, or phragmites; coastal marshes with Spartina. Winter migrants occur frequently in coastal brackish marshes.

behavior

Active and noisy, moving rapidly among reeds, often clinging spread-eagled to two separate stems. The bird is highly territorial and predatory on eggs, both of its own species and of others, such as red-winged blackbirds. Song is a characteristic metallic rattle, sometimes uttered at night. There are many distinctive patterns of songs, with major differences between eastern and western populations.

feeding ecology and diet

Food is mainly invertebrate, including beetles, bugs, dragonfly larvae, spiders, etc. Predated eggs may be partially eaten. Feeds from the water level to the tops of reeds, but usually stays fairly low.

reproductive biology

Exhibits two features found in many other wren species to a high degree, multiple nest-building and polygamy. The nest is a domed structure with a side entrance usually about 3 ft (1 m) above water level. It is made of strips of leaves and grass and lined with down. Eggs number three to 10, usually four to six, fewer in southern populations. They are brown with darker speckles, rarely white. Incubation is by the female, for 13–16 days; young fledge in 13–15 days. Rate of polygamy varies among different populations; may be more than 50% in central Canada, with a significant number of trigamists.

conservation status

Not threatened. Can be common in suitable habitat. Can reach high densities of up to 75 males per acre (190 per ha) in prime habitat. Much habitat loss is due to swamp drainage; conversely, recent water impoundments may create habitat.

significance to humans

Has been and continues to be an intense object of research because of its complex song patterns and interesting breeding behavior.

Zapata wren

Ferminia cerverai

taxonomy

Ferminia cerverai Barbour, 1926, Santo Tomás, Ciénaga de Zapata, Cuba.

other common names

English: Cuban marsh wren, Cervera's wren; French: Troglodyte de Zapata; German: Kubazaunkönig; Spanish: Fermina.

physical characteristics

6.2–6.5 in (15.5–16 cm). Weight: no data. Quite unlike any other wren, with very short wings, long tail, and sturdy legs. Crown is blackish brown; back is brownish with numerous fine bars on back and tertial feathers. Tail is long and fluffy with numerous fine dark bars; underparts are whitish buff, darker

below, the flanks with dark barring. Eyes are clear brown; bill is dark brown with paler base; legs are brownish. Sexes are identical. Juveniles are similar to adults, but with fine speckles on throat and more diffuse barring on flanks.

distribution

Confined entirely to the Ciénaga de Zapata, southwest Cuba. Originally entirely in the vicinity of Santo Tomás; recently small additional populations discovered 9–12 mi (15–20 km) from Santo Tomás.

habitat

Restricted to savanna swampland, with saw grass, rushes, and scattered bushes. Seems to prefer drier areas where it can forage on the ground.

behavior

A very poor flyer. Is quarrelsome and prone to drive off much larger species. Is rather secretive, though it frequently sings from low bushes. Song is a series of gurgling whistles mixed with harsher churring notes. Some dispute as to whether females sing; the female song is stated to be shorter and higherpitched than that of the male.

feeding ecology and diet

Food is varied for a wren; invertebrates such as crickets, caterpillars, flies and spiders, snail eggs, and slugs are eaten. Also takes Anolis lizards, some up to 4 in (10 cm) in length, and some vegetable matter. Forages low in vegetation, but also takes much from the ground.

reproductive biology

A nest was not discovered until 1986, and by 2001 only four had been described. The nest is a ball of saw grass leaves situated in saw grass, with a side entrance hole. It occurs 20–28 in (50–70 cm) above the ground. Eggs number two and are white. Incubation is by the female alone; incubation and fledging periods are unknown. Breeding season extends from January to July; the species may be double-brooded. It is not known whether polygamy occurs.

conservation status

Endangered. The bird is extremely restricted in range. Original range was only 5 sq mi (13 km²), but recently other populations were discovered up to 12 mi (20 km) away. Even within this range, the birds are rather sparse. In the late 1970s no birds could be located and it was feared extinct; present best estimates (April 2000) are of 80–100 pairs. Threats to survival include grass fires and predation by introduced mongooses.

significance to humans

None known.

Bay wren

Thryothorus nigricapillus

taxonomy

Thryothorus nigricapillus Sclater, 1860, Nanegal, Pichincha, Ecuador.

other common names

French: Troglodyte á tête noir; German: Kastanienzaunkönig; Spanish: Cucarachero Cabecinegro, (Panama) El Guerrero.

physical characteristics

5.8 in (14.5 cm). 0.78 oz (21.9 g). Strikingly marked, with black head, white facial markings, chestnut back, and heavily

barred wings and tail. Central American populations have a white throat and unbarred chestnut belly; the South American races are heavily barred with black from the upper chest to the lower flanks. Eyes are brown; bill is blackish with pale orange-yellow base; legs are blackish. Sexes are similar. Juveniles have less clear-cut facial markings, and colors are generally somewhat less rich.

distribution

Caribbean slope of Central America from central Nicaragua and Costa Rica to Panama; both drainages from central Panama to Colombia, western Colombia along Pacific slope to southern Ecuador.

habitat

Edges of humid forest, generally absent from forest interior; Heliconia thickets. Occurs from sea level to 3,600 ft (1,100 m).

behavior

Found in pairs, low in thick vegetation; rather secretive. It is territorial throughout year; both sexes sing and defend territory. Song is a series of varied, loud, ringing whistles. Males may sing on their own, but antiphonal song with female is frequent. The female always initiates a song duet.

feeding ecology and diet

Food is entirely invertebrate, including spiders, beetles, roaches, earwigs, etc.

reproductive biology

Nest, built by both sexes, is an elbow-shaped construction made of grass and vine tendrils, placed in vines or crotches of shrubs at heights of 3–16 ft (1–5 m). Eggs number three and are white with cinnamon speckles. Incubation and fledging periods are not recorded. Breeding season protracted. In Panama it occurs from February to November, in Colombia from January to August.

conservation status

Not threatened; substantial areas of habitat have been lost, however.

significance to humans

None known.

Gray-breasted wood wren

Henicorhina leucophrys

taxonomy

Troglodytes leucophrys Tschudi 1844, Montaña del Vitoc, Junín, Peru. 18 subspecies recognized.

other common names

English: Highland wood wren; French: Troglodyte à poitrine gris; German: Einsiedlerzaunkönig; Spanish: Saltapared-selvatico Pechigris.

physical characteristics

4–4.5 in (10–11.5 cm). The bird is a large-headed plump wren with a short tail and sturdy legs, chestnut-brown above, and gray below with brownish buff lower flanks. Sides of face are strikingly marked with black and white streaks; eyestripe is black; supercilium is white; crown is blackish; throat is grayish white. Flight feathers are chestnut-brown with narrow blackish bars. Eyes are reddish brown; bill is black with dark gray base; legs are brownish black. Male and female are identical in

plumage; juvenile is similar to adults but with the facial pattern less well-defined. There is considerable variation in plumage between different subspecies.

distribution

Disjunct distribution in highlands of Central and South America, separated by unsuitable lowland areas, from central to southern Mexico through Guatemala, Honduras, Nicaragua, Costa Rica, and Panama; Andes and adjacent mountain ranges from northern and central Venezuela through Colombia south to central Bolivia.

habitat

Humid mountain forests, usually above 4,900 ft (1,500 m) but rarely as low as 1,300 ft (400 m), up to 12,500 ft (3,800 m). Occupies several different forest types, including mixed oak and pine woodland, bamboo thickets, and second growth, up to the lower edge of páramo (high altitude heathland).

behavior

Territorial; lives in pairs or family groups. Is very secretive and usually keeps to lower levels of vegetation. Song is a magnificent series of loud ringing whistled phrases, uttered by both sexes in duet. Roosts in pairs or family groups, in nests built for that purpose. Form of roosting nest is identical to that of breeding nest.

feeding ecology and diet

Feeds in lower levels of dense vegetation, actively moving around and probing into leaf-litter and tangles. Diet apparently entirely invertebrate; no evidence that any vegetable matter is taken.

reproductive biology

Nest, built of roots, plant fibers, and moss, is a globular structure with an antechamber leading to a rounded chamber, placed in low vegetation including bamboo thickets. Both sexes build the nest. Eggs number two and are immaculate white. Incubation is by the female only, for 19–20 days. Young are fed by both sexes for 17–18 days. Breeding season depends on geographic location. In Costa Rica breeding occurs late March to early June, in Colombia December to June. Probably multiple-brooded.

conservation status

Not threatened. Much habitat has been lost to agriculture and logging, but large areas remain; some are protected by reserve status.

significance to humans

None known.

House wren

Troglodytes aedon

taxonomy

Silvia domestica Wilson, 1808; suppressed in favor of Troglodytes aedon, Vieillot, 1809. Three subspecies recognized (Clements).

other common names

French: Troglodyte familier; German: Hauszaunkönig; Spanish: Saltapared Cucarachero.

physical characteristics

4.6–5 in (11.5–12.5 cm). Weight 0.28–0.40 oz (8–11 g). A rather plain gray-brown wren without prominent markings.

Crown and nape are medium-brown; back and rump are reddish brown; wings and tail have narrow dark barrings. Face is gray-brown with ill-defined pale supercilium; throat and chest are buffy-white; belly and flanks are buffy-red. Eyes are brown; bill is dusky-brown above and pale horn-gray below; legs are dark brown. Sexes are similar. Juvenile has dusky mottles on breast.

distribution

Breeds across North America from New Brunswick south to California, west to central Alberta and southern British Columbia and south to California. Winters almost entirely south of breeding range, from South Carolina westwards to southern Arizona, south through Mexico to Oaxaca.

habitat

Partially open country with brushy areas, abandoned farmland, forest edges, and well-vegetated suburban areas; in western North America in open deciduous and coniferous forest.

behavior

Very territorial in breeding season. Not particularly secretive, especially when singing. Frequently destroys the eggs of cavity-nesting birds, such as the prothonotary warbler and Bewick's wren. Song is a long series of rapid notes, not particularly tuneful, mostly on one pitch then descending at end. Both sexes sing.

feeding ecology and diet

Most often forages low in tangled vegetation. Food is mainly invertebrate, including spiders, caterpillars, bugs, etc. Also eats a small amount of vegetable matter.

reproductive biology

Is a cavity nester, using old woodpecker holes, tree cavities, disused hornets' nests, old nests of northern oriole or cliff swallow, but increasingly using nest boxes and other artificial sites. Nest has a coarse twig base with a cup lined with hair, wool, and feathers. Eggs number four to eight, rarely three to 10. They are whitish with small spots of reddish brown. Incubation is by the female alone for 12–14 days; young are fed by both sexes for 16–18 days. Single-brooded in Canada, double-brooded or rarely triple-brooded in southern parts of the range. Generally monogamous, but polygyny does occur regularly.

conservation status

Not threatened; populations augmented by provision of nest boxes and abandonment of marginal farmland.

significance to humans

Well-known and popular. Due to the readiness with which it takes to nest boxes, is one of the best-studied of North American passerines.

Winter wren

Troglodytes troglodytes

taxonomy

Motacilla troglodytes Linnaeus, 1758, Sweden. 44 subspecies recognized.

other common names

English: Wren, northern wren, holarctic wren; French: Troglodyte mignon; German: Zaunkönig; Spanish: Saltapared Invernal, Cochín.

physical characteristics

3.6–4 in (9–10 cm). Weight 0.26–0.39 oz (7.5–11.0 g). A very small, short-tailed, and heavily barred wren. Upperparts are warm dark brown, with conspicuous narrow dark bars on wing and tail feathers. Chin and throat are grayish brown, becoming more reddish lower; flanks are deep reddish brown with darker bars. Eyes are brown; bill is brown with paler base; legs brown. Sexes are similar. Juvenile has obscure mottles on chest, and flank bars are less distinct.

distribution

The most widespread of the wrens, found in four continents. North America, breeding range from Alaska, the Aleutian Islands south in mountains to California, eastward across Canada to Newfoundland and south in mountains to Georgia; winter to northern Mexico. Old World from Iceland and Scandinavia

south to Spain, Morocco, Algeria, and Libya; eastward to Russia, Caucasus, Turkey, and Iran; central Asia from Afghanistan to eastern Siberia, Japan, China, and Taiwan, including many offshore islands in Europe and east Asia.

habitat

Extremely varied habitat. In North America, occurs most often in cool forested areas, especially coniferous. In Europe and Asia, occurs in various types of bush and woodland, including deciduous woods with extensive undergrowth; also in suburban areas and treeless offshore islands with low scrubby vegetation. Sea level to 13000 ft (4000 m) in central Asia.

behavior

Territorial in breeding season, but will sometimes roost communally in winter, with several dozen birds crammed in layers into a suitable cavity. Spends most of time down in vegetation, hopping mouse-like through dense tangles; flights are always low and short, between adjacent cover. Song is loud and vehement, a prolonged series of trills and clear notes, much sweeter and purer than song of the house wren.

feeding ecology and diet

Not known.

reproductive biology

Nest is a domed structure with side entrance, usually in dense vegetation or cavities; island races may nest in crannies in rock-faces or ruined buildings. Eggs number five to eight, rarely three to nine. They are white with red-brown speckles; some Aleutian races may lay white eggs. Incubation is by the female for 16 days; young are fed by both parents for 14–19 days. Usually double-brooded. Polygyny is frequent but varies among races. Males build many surplus nests; the female selects the one to be used for breeding and adds the lining.

conservation status

Not threatened. Generally common or abundant over much of its range; populations in Britain fluctuate wildly, being decimated by a severe winter but bouncing back very rapidly. Some island races have very small populations that may fluctuate quickly.

significance to humans

A familiar and popular bird, it is the subject of extensive folklore in many countries, well enough known to be among the few birds with a given name in English, Jenny Wren.

Black-capped donacobius

Donacobius atricapillus

taxonomy

Turdus atricapilla Linnaeus, 1766, location in error, actually eastern Brazil.

other common names

English: Black-capped mockingthrush; French: Troglodyte à miroirs; German: Rohrspottdrossel; Spanish: Paraulata de Agua, Donacobio.

physical characteristics

8.5–9 in (21–22 cm); 1.1–1.5 oz (31–42 g). Unique and unmistakable. Crown, nape, and shoulders are glossy black; back is browner; rump is olive-brown. Tail feathers are black with conspicuous white tips. Wings are blackish with conspicuous

white flash at the base of primaries. Underparts warm yellow buff with black bars on flanks. Eyes are bright yellow; legs are dusky green. Has a distendable yellow cheek pouch.

distribution

Panama (Darién) through lowland South America east of the Andes to coastal Brazil and northern Argentina

habitat

Brushy vegetation over slow-moving rivers and ponds; occurs at sea level to rarely 2,000 ft (750 m), usually lower.

behavior

Demonstrative and noisy. Pairs indulge in loud ritualized displays, advertising the white wing-flashes and tail edgings by spreading the wings and tail. Song is a series of loud whistles. Both sexes sing in antiphonal style. Female song has a lower, grating quality not found in the male's contribution. Other members of a nesting group may also join in. The bird is territorial, with the territories often being linear along a marsh edge.

feeding ecology and diet

Not known.

reproductive biology

A cooperative breeder; a nesting pair may have up to two additional helpers, which are usually young from the previous year or two. Pairs with no assistants rear only one young bird, while helpers can increase the number to two young. Nest is an open cup, usually built over or near water. Eggs usually number two in Venezuela, in Brazil frequently three. They are purplish white, covered with reddish or purplish spots and blotches. Incubation is by the female alone for 16–18 days; young are fed by both parents and by helpers, fledging at 17–18 days. Single-brooded. Adults keep young in nest cool by soaking their body feathers in water and wetting the nestlings.

conservation status

Not threatened. Common or abundant over much of its range. Although marsh-drainage may destroy habitat, the species will colonize suitable vegetation arising around artificial water impoundments.

significance to humans

For two hundred years has provided much diversion and entertainment for taxonomic ornithologists, a process that will doubtless continue.

Resources

Books

Anderson, A.H., and A. Anderson. The Cactus Wren. Tucson: University of Arizona Press, 1973.

Armstrong, E.A. The Wren. London: Collins, 1955.

Brewer, D., and B.K. MacKay. Wrens, Dippers and Thrashers. New Haven and London: Yale University Press and A&C Black, 2001.

Hejl, S., and J.A. Holmes. "Winter Wren (Troglodytes troglodytes)." In The Birds of North America, ed. F. Gill and A. Poole. Philadelphia and Washington, DC: The Academy of Natural Sciences and the American Ornithologists' Union, 2000.

Johnson, L.S. "House Wren (Troglodytes aedon)." In The Birds of North America, ed. F. Gill and A. Poole. Philadelphia and Washington, DC: The Academy of Natural Sciences and the American Ornithologists' Union, 1998.

Raffaele, H., J. Wiley, O. Garrido, A. Keith, and J. Raffaele. A Guide to the Birds of the West Indies. Princeton: Princeton University Press, 1998.

Ridgely, R.S., and G.E. Tudor. The Birds of South America. Vol. 1. Austin: University of Texas Press, 1989.

Periodicals

Atkinson, P.W., M.J. Whittingham, H. Gómez de Silva Garza, A.M. Kent, and R.T. Maier. "Notes on the Ecology, Conservation and Taxonomic Status of Hylorchilus Wrens." Bird Conservation International 3 (1993): 75–85.

Joyce, F.J. "Nesting Success of Rufous-Naped Wrens (Campylorhynchus rufinucha) is Greater Near Wasps' Nests." Behavioral Ecology and Sociobiology 32 (1993): 71–77.

Kiltie, R.A., and J.W. Fitzgerald. "Reproduction and Social Organisation of the Black-Capped Donacobius (Donacobius atricapillus) in Southern Peru." Auk 101 (1993): 804–811.

Verner, J. "Evolution of Polygamy in the Long-billed Marsh Wren." Evolution 18 (1964): 252–261.

Woods, R.W. "Cobb's Wren Troglodytes (aedon) cobbi of the Falkland Islands." Bulletin of the British Ornithologists' Club 113 (1993): 195–207.

David Brewer, PhD