Systematics

Variation is considerable across the wide geographic range of Black-faced Antthrush, chiefly in the form of plumage color and pattern; size varies little, with birds in Costa Rica averaging larger than those in other regions but otherwise relatively uniform body size across the whole of the species’ distribution. Certain plumage features define subspecies groups (see below) defined by primary song. Birds of northern Middle America are characterized by having both rufescent on the sides of the neck that contrasts with the brownish gray hindneck, and the undertail coverts and vent are devoid of or only faintly washed with tawny or cinnamon. Birds from southern Central America southeast into northern Colombia and northwestern-most Venezuela lack the contrasting rufescent collar on the neck and have the undertail coverts washed extensively and boldly with cinnamon. Moreover, the black throat is edged in cinnamon and the breast medium gray, in contrast to birds through the rest of South America, which lack the cinnamon edge to the black throat and have the breast distinctly darker, being a more sooty gray.

Subspecies
Fourteen subspecies, following Krabbe and Schulenberg (2003)—albeit with species-level taxonomy of the American Ornithologists’ Union Check-list of North American Birds (see Systematics)—diagnosed by plumage color and pattern and falling into three groups (Fig. 1; Dickinson and Christidis 2014) defined chiefly by primary song (see Vocalizations).

Black-faced Antthrush (Mayan) Formicarius analis [moniliger Group]

Occurs in Middle America and northern Central America; the song is a long monotone. Three subspecies:

F. a. moniliger Sclater, 1856. Resident in s. México south of the Isthmus of Tehuantepec [type locality = Córdova, Veracruz, Mexico]. Breast sooty gray; sides of neck rufescent, contrasting with brownish gray hindneck; undertail coverts not or only slightly washed with tawny or cinnamon; distinct rufescent collar across foreneck; mantle dark chestnut-brown.

F. a. pallidus (Lawrence, 1882). Resident on the Yucatan Peninsula, including in the Petén of northern Guatemala [type locality = Yucatán, Mexico]. Like F. a. moniliger, but much paler, with the breast light drab gray and the mantle light olive brown.

F. a. intermedius Ridgway, 1908. Resident in northern Central America from southern Belize through eastern Guatemala to central Honduras [type locality = vic. Manatee Lagoon, Belize]. Like F. a. moniliger, but paler, with the breast mouse gray and the mantle umber.

Black-faced Antthrush (Central American)  Formicarius analis [hoffmanni Group]

Occurs in southern Central America and northwestern South America; the song is a short monotone. Six subspecies:

F. a. umbrosus Ridgway, 1893. Resident on the Gulf slope from southern Honduras through Nicaragua to eeastern Costa Rica [type locality = Talamanca, Costa Rica]. Like F. a. moniliger, but lacks rufescent collar across foreneck and breast slatier (less sooty). Placement in this group is assumed and await analysis of songs.

F. a. hoffmanni (Cabanis, 1861). Resident on the Pacific from central Costa Rica, east, including on the Osa Peninsula, to western Panama [type locality = Costa Rica]. Similar to F. a. umbrosus, but undertail coverts washed extensively with dark cinnamon; also, forehead pale rufescent or cinnamon, contrasting with brown crown; mantle brownish; white loral spot small or absent; averages larger (see Ridgway 1911).

F. a. panamensis Ridgway, 1908. Resident in the Darién of Panamá and in adjacent northwestern Colombia [type locality = Lion Hill Station, Panama]. Like F. a. hoffmanni, but undertail coverts paler and tawnier and breast brownish, with distinct olive tones; averages smaller.

F. a. virescens Todd, 1915. Resident in the Santa Marta Mts. of northern Colombia [type locality = Fundación, Columbia]. Like F. a. panamensis, but mantle olivaceous.

F. a. griseoventris Aveledo and Ginés, 1950 – Resident in the western Maracaibo Basin of Venezuela [type locality = de Kunana, Serranía del Perijá, Venezuela]. Similar to F. a. virescens, but breast pure gray (not brownish). Placement of this and the following subspecies in this group is tentative pending analysis of primary song.

F. a. saturatus Ridgway, 1893. Resident in Venezuela north of the Orinoco and on Trinidad [type locality = Princesstown, Trinidad]; also in the Magdalena Valley of Colombia. Similar to F. a. griseoventris, but breast brownish gray and mantle rufescent-brown (less olive), and black throat edged cinnamon.

Black-faced Antthrush (Black-faced) Formicarius analis [analis Group]

Occurs in Amazonia and on the eastern Guianan Shield; the song is long and multitoned. Five subspecies:

F. a. connectens Chapman, 1914. Resident in eastern Colombia, east of the Andes [type locality = Villavicencio, Columbia]. Like F. a. saturatus, but black throat lacking cinnamon edge, breast darker and less brown (more slate gray), and mantle more olive (less rusty); averages smaller.

F. a. crissalis (Cabanis, 1861). Resident on the Guianan Shield from Guyana east through Suriname to French Guiana [type locality = Roraima, Guyana]. Similar to F. a. saturatus, but white loral spot large and conspicuous, ventrum contrasty, the brownish gray breast blending to a whiter vent, and undertail coverts tawny (less rusty); also, rump and uppertail coverts brownish and auriculars vinaceous rust.

F. a. zamorae Chapman, 1923. Includes F. a. olivaceus Zimmer, 1931. Resident in Ecuador, northern Perú, and northwestern Brazil, north of the Amazon [type locality = Zamora, Ecuador]. Similar to F. a. connectens, but ventrum darker still (a sooty-slate) and undertail coverts rich chestnut (less tawny); averages slightly larger.

F. a. analis (d’Orbigny and Lafresnaye, 1837). Resident in western Amazonia south of the Amazon [type locality = Yuracares and Chiquitos, Bolivia]. Like F. a. zamorae, but gray breast paler (less sooty) and undertail coverts paler (more tawny).

F. a. paraensis Novaes, 1957. Resident in eastern Amazonia, east of the Tapajós [type locality = Socêgo, Fóz do Rio Traquateua, Município de Ananindeua, Parâ, Brazil]. Similar to F. a. crissalis, but rump and uppertail coverts ferruginous (more rufescent, less brown), mantle slightly more olivaceous, and auriculars pure vinaceous (lacking rusty tones).

Avian taxonomists recognized a broadly inclusive family Formicariidae for many decades, a family that included all antthrushes, antpittas, and non-terrestrial antbirds, from antshrikes to antwrens. Molecular systematics altered that concept when it was found that these myriad birds did not form a natural clade (Chesser 2004, Rice 2005). Instead, the Formacariidae sensu stricto, which includes only the antthrushes of the genera Formicarius and Chamaeza, are sister to a radiation of "furnarioids", the former broad family Furnariidae that is either split into a narrower Furnariidae (ovenbirds, spinetails, foliage-gleaners, and allies) plus the families Scleruridae (leaftossers and miners) and Dendrocolaptidae (woodcreepers) (Moyle et al. 2009, Ohlson et al. 2013) or with the broad Furnariidae subdivided into those respective subfamilies (e.g., Remsen et al. 2015).

Species limits within Formicarius analis are an open question. On the basis of consistent differences in song, Howell (1994) argued that the moniliger group was a species distinct from the hoffmanni group, a taxonomic recommendation followed in the Handbook of the Birds of the World (Krabbe and Schulenberg 2003) and the Complete Checklist of the Birds of the World (Dickinson and Christidis 2014) even though Howell failed to consider the equally marked difference between songs of the hoffmanni group and analis group, to say nothing of the (broadly) more similar songs of the moniliger group and analis group. Field work on habitat use and mate choice is needed in contact zones to assess the extent to which vocal groups behave as biological species (see Priorities for Future Research).