White-browed Antbird

The white-browed antbird (''Myrmoborus leucophrys'') is a species of perching bird in subfamily Thamnophilinae of family Thamnophilidae, the "typical antbirds". It is found in every mainland South American country except Argentina, Chile, Paraguay, and Uruguay.

Taxonomy and systematics

The white-browed antbird was described in 1844 as ''Pithys leucophrys''. It eventually was determined to have these four subspecies:

*''M. l. erythrophrys'' ( Sclater, PL, 1855)
*''M. l. leucophrys'' (Tschudi, 1844)
*''M. l. angustirostris'' (Cabanis, 1849)
*''M. l. koenigorum'' O'Neill & Parker, TA, 1997

Other subspecies and the geographical redistribution of these four have been suggested but as of 2024 not accepted.Zimmer, K. and M.L. Isler (2020). White-browed Antbird (''Myrmoborus leucophrys''), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.whbant6.01 retrieved March 15, 2024 Authors have suggested that that some of the subspecies might better be treated as full species.Zimmer, K.J., and M.L. Isler. 2003. Family Thamnophilidae (typical antbirds). Pp. 448-681 ''in'' "Handbook of the Birds of the World, Vol. 8. Broadbills to Tapaculos." (J. del Hoyo, A. Elliot, and D.A. Christie, eds.). Lynx Edicions, Barcelona.

Description

The white-browed antbird is long and weighs . Adult males of the nominate subspecies ''M. l. leucophrys'' have the eponymous white forehead and supercilium. They are otherwise mostly dark bluish gray that is darkest on their wings and tail and lightest on their crissum. Their face below the white, their chin, and their throat are black. Adult females have a cinnamon to yellow-buff forehead and supercilium. Their crown is olive-brown with a reddish tinge and the rest of their face is black. They have olive-brown upperparts. Their wings and tail are dark yellowish brown with pinkish to pale buff-brown tips on their wing coverts. Their throat and underparts are mostly white with some blackish gray on the sides and light olive-gray flanks.Schulenberg, T.S., D.F. Stotz, D.F. Lane, J.P. O’Neill, and T.A. Parker III. 2010. ''Birds of Peru''. Revised and updated edition. Princeton University Press, Princeton, New Jersey. Plate 170.

Males of subspecies ''M. l. angustirostris'' are similar to nominate males but paler. Females have a paler supercilium than the nominate and paler (almost white) tips on the wing coverts. Males of ''M. l. erythrophrys'' have a wider white forehead band and supercilium and a less well-defined black throat than the nominate. Females have a darker and redder supercilium that has little contrast from the crown. Males of ''M. l. koenigorum'' have an entirely white crown and the black of their throat extends onto the breast. Females are similar to ''erythrophrys'' females.

Distribution and habitat

The white-browed antbird has a curious distribution across the northern Amazon Basin and the Guianan Shield and in the southern Amazon Basin, but not in a large area of Amazonia between them. The subspecies are found thus:

*''M. l. erythrophrys'': east slope of the Andes from northwestern Venezuela south into Colombia to the Putumayo River
*''M. l. leucophrys'': from the Putumayo in extreme southern Colombia south on the east slope of the Andes of eastern Ecuador and eastern Peru into northeastern Bolivia, and east across much of southern Amazonian Brazil south of the Amazon
*''M. l. angustirostris'': from southern Venezuela east across the Guianas and northern Brazil north of the Amazon to the Atlantic in Amapá state
*''M. l. koenigorum'': upper valley of the Huallaga River in Peru's Department of Huánuco

The white-browed antbird uses various habitats in different parts of its range. In the Amazon Basin it typically occurs near water, using both '' várzea'' and transitional forests. There it favors heavy shrub cover and '' Heliconia'' thickets and sometimes bamboo. Subspecies ''M. l. angustirostris'' is often found in similar habitat but about equally on the edges and in overgrown clearings of ''terra firme'' forest. A relatively small part of the ''angustirostris'' population in southern Venezuela also occurs on shrubby and stunted woodlands on white-sand soils bordering savanna. Along the slopes of the Andes, the other three subspecies use a similar mix of habitats as most of ''angustirostris''. In elevation the species occurs up to in Colombia, in Ecuador, in Peru, in Venezuela, and perhaps to in Brazil.

Behavior

Movement

The white-browed antbird is believed to be a year-round resident throughout its range.

Feeding

The white-browed antbird feed on a wide variety of insects and spiders. It typically forages singly, in pairs, or in small family groups in dense vegetation, mostly on the ground or within about of it and rarely up . It hops and makes short flights between feeding stops, bobbing its tail. It captures prey by gleaning, jumping, lunging, and making short sallies from a perch; it also drops to the ground to snatch prey. It regularly attends army ant swarms to capture prey fleeing the ants, but is subordinate to obligate ant-followers. It seldom joins mixed-species feeding flocks.

Breeding

The white-browed antbird's breeding season has not been defined but in Peru it includes May. The one known nest was made from bamboo leaves and placed on the ground. It contained two brown-specked whitish eggs. Nothing else is known about the species' breeding biology.

Vocalization

The male white-browed antbird's song is "a long (e.g. 4 seconds) trill typically increasing in intensity and pace initially, dropping slightly in pitch at end"; the female's is "shorter and often rising in pitch initially". The subspecies' songs differ greatly in their pace. The species' calls include a short whistle that varies geographically from clear to nasal or burry. They also make a "short 'chip' (may not occur in all regions), and short, rather high-pitched rattle diminishing in intensity and pitch and typically repeated rapidly at short intervals".

Status

The IUCN has assessed the white-browed antbird as being of Least Concern. It has a very large range; its population size is not known and is believed to be ddecreasing. No immediate threats have been identified. It is considered fairly common across its range. "The species’ ability to occupy a variety of second-growth habitats renders it less vulnerable to disturbance than are many other antbird species. Populations confined to lower Andean slopes and inter-Andean valleys potentially at greatest risk; not only are their ranges more restricted, but foothill forest throughout Andes is being cleared for agriculture and human settlement at alarming rates."

References

{{Taxonbar, from=Q1266655

white-browed antbird
Birds of the Amazon rainforest
Birds of the Guiana Shield
white-browed antbird
Taxonomy articles created by Polbot