Myrmotherula omissa Todd, 1927, subspecies elevated to species

Eastern Gray Antwren

Includes the study populations designated omissa- E and omissa- W in the analysis.

Diagnosis. Myrmotherula omissa is distinguished from M. cinereiventris and M. menetriesii s.s. by vocalizations and plumage. The structure of individual notes distinguishes Songs of Myrmotherula omissa from those of M. cinereiventris (Fig. 6), and the sequence of abrupt notes and longer downslurred notes in Long Calls of Myrmotherula omissa differs from those in Long Calls of both M. cinereiventris and M. menetriesii (Fig. 7). Males of omissa differ from M. menetriesii s.s. by the absence of black patches on throat and upper breast.

Description of female plumage. Female upperparts are Olive Gray (generally 5Y4/1 for omissa- E and 5Y4/2 for omissa –W, but with intermediates); underparts typically Brownish Yellow (10YR6/8) but sometimes as light as Yellow Ochre (10YR7/6) and therefore not entirely distinguishable from those of menetriesii s.s. or cinereiventris, but tend to be paler on chin and sides of head.

Distribution. Bounded on the north by the Amazon River, forest limits in central Isla Marajó, and the Atlantic Ocean; on the east by the Rio Pindaré, Maranhão; on the southeast by Amazonian forest limits; and on the southwest in the region between the lower Rio Madeira/lower Rio Aripuanã/lower Rio Roosevelt and the headwaters of the Rio Teles Pires.

Remarks. Some male specimens of M. omissa have a scattering of black spots on the throat and upper breast. Specific status for Myrmotherula omissa is reinforced by mtDNA genetic distances of ~5.9% among the three species that formerly constituted M. menetriesii. The intersection of the geographic ranges of M. omissa and M. menetriesii berlepschi is unclear and awaits further field exploration. The genetic analysis identified mtDNA genetic distances of 1.6% between study populations omissa -E and omissa- W, but no diagnostic vocal characters were found, although female plumage may differ.

Myrmotherula omissa (198 recordings).

BRAZIL: AMAZONAS: Rio Acarí 3; Pousada Aripuanã 1; R bank Rio Aripuanã opposite Nova Olinda 1; Rio Bararati 4; Barra de São Manuel 1; Igarapé Boa Esperança 1; Borba 1; Igarapé da Cabaça, 3; Rio Cararucu 1; Rio Ipixuna 1; 52 km W Jacareacanga 1; Pousada Jurumé 4; Rio Mapía 33 km S of Borba 3; mouth of Rio Palomitas 2; Rio Parauri near Cachoeira Tambo 4; Igarapé Pedral 1; Ponto Nove (Rio Sucunduri) 1; Ponto Oito (Rio Sucunduri) 1; Prainha Nova 1; Pousada Rio Roosevelt (R bank) 2; Ramal Sauré 2; Rio Sucunduri near BR 230 13; Rio Sucunduri near mouth Rio Acari 3; Igarapé Tucumã 1; MATO GROSSO: Alta Floresta 5; Serra dos Caiabis 1; Rio Cristalino 20; mouth of Rio São Tome 1; PARÁ: P. N. Amazonia 3; Aveiro 1; Belterra 1; Boim 4; Caxiuanã 23; Serra dos Carajás 17; Igarapé Guará 1; Rio Itacaiúnas 1; km 220–235 S of Itaituba 5; Jacareacanga 3; Mirituba 3; Paragominas 8; Vale de Rio Paraupebas 4; Porto do Meio 1; Fazenda Rio Capim 14; Riosinho (R. I. Kayapó) 8; Fazenda Rozinho 6; Senador José Porfirio 1; F. N. do Tapajós 3; Pousada Thaimaçu 1; Vila Braga 3; R bank Rio Xingu 15 km S of Altamira 1; TOCANTINS: Tocantins 1.

Myrmotherula omissa.

BRAZIL: Pará: 52 km SW Altamira 1♀; Belém 1♀, 1♂; Benevides 1♀, 4♂; Caxiuana 1♂; Mirituba 2♀, 1♂; Tauari 3♀, 1♂.