Des Murs's Wiretail

Des Murs's wiretail (''Sylviorthorhynchus desmursii'') is a small passerine bird of southern South America which belongs to the ovenbird family Furnariidae. Molecular phylogenetics places it within the Synallaxinae and indicates that the genus diverged from the '' Leptasthenura'' about 14-15 million years ago.

Description

It is long, with the very long tail accounting for about two-thirds of this, but weighs as little as .Johnson, Alfredo William (author) and Goodall, J.D. (illustrator); ''The birds of Chile and adjacent regions of Argentina, Bolivia, and Peru'', Volume II; pp. 171-173. The tail consists of just six feathers which are very narrow and filament-like: so few rectrices are elsewhere seen only in the emu-wrens of Australia. The two central feathers are greatly elongated while the two outer feathers are very short. The plain plumage is reddish-brown above, paler on the underparts. There is a pale stripe above the eye. The bird is small and rounded with a very fine bill. The song is fast and high-pitched.

Distribution and habitat

It is found in western Argentina from Santa Cruz Province north to San Juan and in southern and central Chile from northern Magallanes to Valparaíso Region. It inhabits dense thickets of ''Chusquea'' bamboo within cool temperate rainforests, occurring from sea-level up to 1,200 metres, but also can occur in early-successional shrublands of highly shade-tolerant Myrtaceae species, chiefly ''Amomyrtus''.Diáz, Iván A., Armesto, Juan J. and Willson, Mary F
“Mating success of the endemic Des Murs’ Wiretail (''Sylviorthorhynchus desmursii'', Furnariidae) in fragmented Chilean rainforests”
/ref> Des Murs's wiretail is also known to occur in dense weedy thickets of plants like gorse over the northern extremity of its range. Even in undisturbed rainforests, however, wiretails use only the low-level shrub and bamboo layer for foraging, never flying higher than above the ground.

Behaviour and ecology

It is very shy and difficult to see, being completely unable to enter areas without dense vegetative overstoreys, and cannot typically use corridors smaller than or fly further than between patches of suitable habitat.Diáz, Iván A., Willson, Mary F., Gehee, Steven M.C. & Armesto, Juan J.
“Observaciones Sobre La Biologia y Conservación del Colilarga (Sylviorthorhynchus desmursii, Furnariidae) en la Isla de Chiloé, Chile”
/ref>

When encountered Des Murs's wiretail can easily be mistaken for a mouse. It has the unique ability among birds to curl up its long tail into a ball when alarmed.

The ball-shaped nest is made of plant fibres and built amongst vegetation close to the ground. Both partners are highly territorial with a territory size of around per pair; however, pairs in territories smaller than are seldom successful at nesting. This territory and the nest site are defended vigorously against conspecifics with a distinctive territorial song, and it is possible that the long tail is used by both sexes as an means of choosing a mate, though no actual tests have been used to determine how wiretails find a mate.

As is typical for south temperate insectivorous birds, during the breeding season of October to February Des Murs's wiretail lays a clutch of two to four eggs, but for the bird's mass these are about the largest eggs of any passerine bird. At long and wide, they weigh twice as much as expected for a 10 gram passerineBased on the formula of egg mass = 0.258''m''^0.73, where ''m'' is body mass. From Rahn, H., Sotherland, P. and Paganelli, C. V., 1985. “Interrelationships between egg mass and adult body mass and metabolism among passerine birds” in ''Journal für Ornithologie'' 126:263-271. and a clutch of four weighs more than the adult female - a feat equalled only by much more fecund kinglets. Little is known about incubation, fledging periods, or postfledging parental care due to the very secretive nature of the species.

References

*Jaramillo, Alvaro; Burke, Peter & Beadle, David (2003) ''Field Guide to the Birds of Chile''. Christopher Helm, London.

External links

Des Murs's wiretail in IBC (Internet Bird Collection

Des Murs's wiretail sounds in Xenocanto

{{Taxonbar, from=Q1263434

Des Murs's wiretail
Birds of Chile
Des Murs's wiretail
Taxobox binomials not recognized by IUCN