| White-throated treerunner | |
|---|---|
.jpeg) | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Family: | Furnariidae |
| Genus: | Pygarrhichas Burmeister, 1837 |
| Species: | P. albogularis |
| Binomial name | |
| Pygarrhichas albogularis (King, 1831) | |
 | |
| White-throated treerunner range | |
Thewhite-throated treerunner (Pygarrhichas albogularis) is aspecies of bird in the familyFurnariidae. It is the only species in thegenusPygarrhichas. The white-throated treerunner is about 15 cm (5.9 in) long, with a stiff and rounded tail. Theupperparts are dark brown, turning red on the lower back and tail and contrasting sharply with the throat and chest of a bright white. The rest of theunderparts are coarsely mottled with white. The bill is long, slightly curved upwards. The general appearance is reminiscent of anuthatch (Sitta spp.), although they are not directly related. Like the Sittidae, Furnariidae tirelessly scours the trunks and branches of old trees for the smallarthropods that make up its food, spiraling up the trunks, or sometimes moving head down. The white-throated treerunner consumes smallinvertebrates found on bark and nests in tree cavities. Outside of the breeding season, it may formmixed-species foraging flocks with other bird species.
The White-throated treerunner inhabits the southern tip of the American continent, inChile andArgentina, fromSantiago andMendoza toTierra del Fuego. It seeks out forests with large trees – the old trunks offer suitable nesting sites – whether they are lowland or highland, dense or open. It was described in 1831 byPhillip Parker King, a British explorer ofPatagonia andTierra del Fuego. Its systematic placement has remained unclear within its family, superficial similarities with other Furnariidae gleaning their food from the bark of trees seem to be the result of anevolutionary convergence.Molecular phylogenies seem to link it to the generaMicroxenops andOchetorhynchus. No subspecies is described. Its range is relatively large and there is no evidence of decline in numbers, so theInternational Union for Conservation of Nature considers this bird to be of "least concern".
The white-throated treerunner was scientifically described in 1831 under theprotonymDendrocolaptes albogularis by the British explorerPhillip Parker King, who visitedPatagonia andTierra del Fuego among other places. Thespecific name,albogularis, means "white-throated" inLatin; the type locality is not known but is supposed to be theStrait of Magellan. In 1837, the Argentine zoologistHermann Burmeister removed the species from the genusDendrocolaptes, which today includes only five species of climbers, and assigned it a separate genus,Pygarrhichas, giving it the novel specific name of "ruficaudis" (from Latin meaning "red-tailed").[2] Burmeister constructs this name from theancient Greek πυγη (pugē) meaning "rump" and αρριχος (arrhikhos) denoting wicker, to refer to the stiffness of the bird's tail helping it progress along trunks.[3]
In 1839, English ornithologistJohn Gould, presumably unaware of King's work,[4] independently described the species inZoology of the Voyage of H.M.S. Beagle asDendrodramus leucosternus (from the ancient Greek for "white-bellied"). He observed the species on theChiloé Island, and found similarities with theEurasian treecreeper (Certhia familiaris) in its behavior.[5] In 1890, English zoologistPhilip Lutley Sclater placed this genus in the now obsolete familyDendrocolaptidae,[6] a position changed by paleornithologistAlan Feduccia in 1973 who placed the genus in its current family,Furnariidae.[7][8] According to theInternational Ornithological Congress and Alan P. Peterson, no subspecies is distinguished.[9][10]
In 1839, Gould mentions that English zoologistGeorge Robert Gray would relate the white-throated treerunner to the genusDendroplex described by English ornithologistWilliam Swainson.[5] In the 2003Handbook of the Birds of the World, Volume 8, American ornithologistJames Van Remsen Jr. explains that while P. albogularis is traditionally related to theXenops sittines and other tree-bark gleaning Furnariidae, plumage and biogeography suggest that these different species are not directly related and that their similarities are merely the result ofconvergent evolution. It has also been suggested that similarities in plumage and foraging behavior may bring the white-throated treerunner closer toSynallaxis of the genusAphrastura.[11]
Twomolecular phylogenies of the family published in 2009, and then one in 2011, negate such relatedness and clarify the evolutionary history somewhat while implying significant classification changes. The naming of a subfamily (that of "Pygarrhichinae") or tribe (that of "Pygarrhichini", within the subfamily Furnariinae) is advanced for aclade that would include the white-throated treerunner, therufous-tailed xenops (Microxenops milleri), species of the genusOchetorhynchus, and would absorb theband-tailed Eremobius (O. phoenicurus) as well as thecrag chilia (O. melanurus), previously placed in themonotypic generaEremobius andChilia respectively.[12][13][14][15]
|
_(15774411279)_(cropped).jpg)
The white-throated treerunner is 15–16 cm (5.9–6.3 in) long on average, with a weight between 20–27 grams (0.71–0.95 oz).[11][16] It has an appearance reminiscent of thenuthatch, with its overall look and plumage, unlike other species in the Furnariidae.[11]Wing chord is from 76–86 mm (3.0–3.4 in), tail is 52–65 mm (2.0–2.6 in), and torso from 20–23.7 mm (0.79–0.93 in).[17] Theiris is dark brown.[11] It has a longbeak, at around 16–23.8 mm (0.63–0.94 in) with a slight upward curve.[16][17] Its upper mandible is dark gray and lower mandible a whitish-pale gray. The feet are dark gray, blackish or brown.[11]
The species is easily recognized by its white throat, contrasting with its upper parts.[17] Its face is blackish-brown and slightly darker than its headcrown, which is a dull brown. The back is a paler chestnut-brown,[11] pulling against the red rump and tail.[17][18] The wingcoverts are dark brown, with red or chestnut brown on the feather edges and tail end. The primaries are darker, the remiges black-brown with light edges and inner primaries marked with a short, light red wing bar. The tail is rounded, with rigidrectrices with shortenedbarbs ending in small spines up to 9 mm (0.35 in) long.[11]
A large white zone covers the treerunner's cheek and throat, descending to the middle of the chest. The rest of the lower parts, to theundertail coverts, are made up of white feathers largely bordered with dark brown, giving an irregularly spotted appearance. Both sexes of adults look similar. The chick is distinguished by anochre-striped crown and back, and often with blackish borders on the throat feathers.[11]
| Songs and calls |
The white-throated treerunner gives off a short and piercing cry, evoking a rapid succession of water droplets.[17] Itscontact call is described as a loud, fast, metallic "kik-ik", "tsi-ik" or "tsik", which is repeated rapidly. The treerunner can also emit a sonorous "peet peet", and during flight, a dry "tic".[11]
Similar in behavior to nuthatches (Sitta spp.), the white-throated treerunner is a restless bird, moving in a jerky manner and changing direction rapidly. The bird may descend from trunks head first. It scours the trunks and large branches of old trees, often spiraling around the trunks,[17] searching for small insects and their larvae in every crevice for food, sometimes tapping lightly with its bill, much like a woodpecker,[19] or digging out larvae from under the bark with its bill.[20] It may use its tail for support, or it may use its tail as a support for the insects. It may use their tail for support, but it also does a lot of tail-first browsing.[11] It explores trunks quickly and spends more time foraging in smaller branches, looking for prey at the base of leaf petioles.[19]
Its diet is little known, consisting ofarthropods including adults and larvae ofbeetles, as well asdiptera.[11][16] A study conducted in the province of Osorno showed that the white-throated treerunner mainly forages on trees such asCoigüe (Nothofagus dombeyi), but alsoNeuquén Roble (N. obliqua),Ulmo (Eucryphia cordifolia), and more generally on dead trees, even when other tree and shrub species are available. These preferences could be explained by the structure of the bark and the greater abundance of accessible insects.[21] In some locations, particularly on islands with no terrestrial predators, the species may also feed on the ground.[17] Outside the breeding season, it may formmixed-species foraging flock with thethorn-tailed rayadito (Aphrastura spinicauda), as well as with thestriped woodpecker (Veniliornis lignarius), and sometimes also with thefire-eyed diucon (Xolmis pyrope),[22]Patagonian sierra finch (Phrygilus patagonicus) and theblack-chinned siskin (Spinus barbatus).[23]
The white-throated treerunner nests in tree cavities. It may nest in the trunks of senescent or fire-damaged trees,[16][18] but is not as successful at this task as other species such as woodpeckers and therefore also reuses existing cavities. Observations of antagonistic behavior by the woodpecker toward other species reusing tree cavities suggest that it competes with these birds in cavity use more than it provides them with new nesting sites by excavating its own hole.[24] A study of the thorn-tailed rayadito to assess whether or not broadcast conspecific songs attracted individuals to a suitable nesting area showed that, on the contrary, cavity-nesting birds-including white-throated treerunners andhouse wrens-avoided competitive areas. The white-throated treerunner, however, readily uses nest boxes.[25]
The nest cavity is usually between 3–8 mm (0.12–0.31 in), above the ground, and is 25–40 cm (9.8–15.7 in), deep. There is no lining other than the chips from the excavation, but a carpet of grasses and feathers has been reported once. The breeding season probably spans the southern spring and summer, with eggs laid in November-December and young hatching in December. The white-throated treerunner is thought to bemonogamous, laying two to three eggs.[11] Eggs preserved at theNatural History Museum in London and measured by English naturalistEugene William Oates are approximately 21.5 mm–22 mm × 16.7 mm–17 mm (0.85 in–0.87 in × 0.66 in–0.67 in).[26] Capture-mark-recapture data from 35 individuals in theCape Horn Biosphere Reserve indicate a longevity of at least 3 years and 8 months.[16]
This species lives in central and southernChile and westernArgentina, fromSantiago andMendoza toTierra del Fuego.[11] It is found in the south of its distribution in the southernmost forest in the world, onHorn Island.[17] It lives from sea level to 1,200 m of altitude,[1][11] populating forests with large trees, whether dense or not, but avoiding young forests.[22] The white-throated treerunner seeks out forests dominated by "false beech" species of the genusNothofagus.[11] It exploits the trunks at mid-height of trees up to the top of the canopy as a small woodpecker would.[17] The species is sedentary, but can be erratic outside the breeding season.[11]
The white-throated treerunner appears in some traditionalYagana stories astatajurj, where it accompanies women and collectsepiphytic fungi of the genusCyttaria (katran in Yagan) from the trunks ofMagellanic Beech (N. betuloides),Lenga (N. pumilio), andÑire (N. antarctica) trees.[17]
The white-throated treerunner needs to have oldsenescent trees available for nesting, a specific and scarce habitat that deserves a conservation effort.[17] However, it is quite common, and present in many protected areas such asVicente Pérez Rosales National Park,Puyehue National Park,Nahuelbuta National Park andLa Campana National Park in Chile, orTierra del Fuego National Park in Argentina.[11] The range of the white-throated treerunner is estimated at 470,000 km2 (180,000 sq mi) and its numbers are believed to be stable; thus, the species is considered of "least concern" by theInternational Union for Conservation of Nature.[1]
