White-flanked Antwren

The white-flanked antwren is 9 to 10.5 cm (3.5 to 4.1 in) long and weighs 5 to 10.6 g (0.18 to 0.37 oz) 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. …

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

M. a. albigula: Caribbean slope of Central America from Honduras south through Nicaragua, Costa Rica, and Panama into northern Colombia, and Pacific slope from Panamá and Darién provinces of Panama south through western Colombia into Ecuador as far as Azuay Province; also a single record from Chiapas, Mexico M. a. melaena: Colombia's isolated Sierra Nevada de Santa Marta; from Colombia east of the Andes and western Venezuela south through eastern Ecuador into northeastern Peru and east in Brazil north of the Amazon to the Rio Negro M. a. heterozyga: from east-central Peru's departments of Ucayali and Madre de Dios east into Brazil south of the Amazon to the Rio Madeira M. a. axillaris: Trinidad and from eastern Venezuela south through western Brazil into northern Bolivia and east through the Guianas and across much of northern Amazonian Brazil M. a. fresnayana: far southeastern Peru's Department of Puno and northwestern and central Bolivia The white-flanked antwren inhabits the understorey and mid-storey of evergreen forest including terra firme, várzea, igapó, and transitional types. It also occurs in secondary woodland. Within these forest types some populations specialize in microhabitats. For instance, in part of its Brazilian range M. a. …

The white-flanked antwren feeds on arthropods, mostly insects and spiders. It forages singly, in pairs, or in family groups, and in most areas usually as part of a mixed-species feeding flock. It typically forages in dense vegetation between about 2 and 12 m (7 and 40 ft) above the ground. It actively seeks prey mostly by gleaning leaves, and also takes prey from vine tangles and along branches by gleaning, reaching, lunging, and with short sallies from a perch. There are records of the species following army ant swarms but for only a few minutes.