White-flanked antwren

The white-flanked antwren (Myrmotherula axillaris) is a species of bird in subfamily Thamnophilinae of family Thamnophilidae, the "typical antbirds". It is found from Honduras to Panama in Central America, in every mainland South American country except Argentina, Chile, Paraguay, and Uruguay, and on Trinidad.

Taxonomy and systematics

The white-flanked antwren was described by the French ornithologist Louis Pierre Vieillot in 1817 and given the binomial name Myrmothera axillaris.

The white-flanked antwren's taxonomy is unsettled. The International Ornithological Committee (IOC) and BirdLife International's Handbook of the Birds of the World assign it these five subspecies:

M. a. albigula Lawrence, 1865
M. a. melaena (Sclater, PL, 1857)
M. a. heterozyga Zimmer, JT, 1932
M. a. axillaris (Vieillot, 1817)
M. a. fresnayana (d'Orbigny, 1835)

The Clements taxonomy adds a sixth subspecies, M. a. luctuosa, that the other two systems treat as a separate species, the silvery-flanked antwren (M. luctuosa). The North and South American Classification Committees of the American Ornithological Society also include the silvery-flanked taxon within the white-flanked antwren. Clements does recognize the taxon as its own "group" within the white-flanked species.

This article follows the five-subspecies model.

Description

The white-flanked antwren is long and weighs with some variation in weight among the subspecies. It is a smallish bird with a short tail. Adult males of the nominate subspecies M. a. axillaris have a dark gray head, neck, back, and rump with a hidden white patch between the shoulders. Their tail is blackish with white tips to the feathers. Their wings are blackish with white tips on the coverts and gray edges on the flight feathers. Their throat, breast, and the center of their belly are black, their flanks the eponymous white, and their crissum gray with black and white tips on the feathers. Adult nominate females have a mottled pale olive-brown face. Their upperparts are olive-brown that becomes reddish yellow-brown on the rump. Their tail feathers are dark brown with light cinnamon-rufous edges. Their wings are dark brown with cinnamon edges on the coverts and light cinnamon-rufous edges on the flight feathers. Their throat and flanks are white, their breast and belly rich buff, their sides olive-brown, and their crissum reddish brown. Juvenile males resemble adult females but with mixed yellow-brown and gray upperparts and wings and mixed white and gray underparts.

The other four subspecies of the white-flanked antwren differ from the nominate and each other thus:

M. a. albigula: male blacker than nominate but variable, with wide white edges on the scapulars; female has grayer upperparts than nominate, with pale buff tips on wing coverts, and paler below with a buff crissum
M. a. melaena: male like albigula; female like nominate but paler
M. a. heterozyga: male slightly paler than nominate with less extensive black underparts; female paler and less rufescent than nominate and with buff tips on the flight feathers
M. a. fresnayana: like heterozyga

Distribution and habitat

The white-flanked antwren ranges from Honduras to central South America. The subspecies are found thus: