Myrmotherula garbei Ihering, 1905

Isler, Morton L., Chesser, R. Terry, Stryjewski, Katherine Faust & Whitney, Bret M., 2025, Systematics of three pan-Amazonian antwren lineages (Aves: Passeriformes: Thamnophilidae: Myrmotherula and Isleria), Zootaxa 5722 (1), pp. 45-78 : 54

Myrmotherula garbei Ihering, 1905 , subspecies elevated to species

Western Long-winged Antwren

Includes the study populations designated garbei and zimmeri in the analysis

Diagnosis. Myrmotherula garbei is distinguished from M. longipennis and M. paraensis by vocalizations and female plumage. The shape of notes in Songs of M. garbei differ from those in Songs of M. longipennis and M. paraensis ( Fig. 2). Furthermore, the pace of M. garbei Songs is significantly slower than the pace of Songs of M. paraensis , and notes in M. garbei . Songs rise in frequency whereas those of M. longipennis decline. Note shapes in Series Calls of M. garbei differ from those of M. longipennis , and note shapes in Multi-note Calls of M. garbei differ from those of M. paraensis ( Fig. 3). Diagnosable plumage differences are limited to females. Principally, the very dark gray upperparts of M. garbei are distinctive, distinguishing this species from both of its sister species, although upperparts of some populations of M. paraensis are a more olive-gray. The color of posterior underparts of M. garbei is similar to that of the breast, in contrast to those of M. longipennis , which are white.

Description of female plumage. Upperparts dark gray tinged olive to olive gray (5Y4/1–4/2), wings and tail very dark olive-gray to dark gray-tinged olive (2.5Y3/1–5Y4/1), and wing edgings pale olive-brown to pale olive-gray (2.5Y5/4–5Y6/2). Underpart colors appear to distinguish two subspecies, but see Remarks. Breast of the nominate form is pale olive yellow (2.5Y7/6) and of zimmeri reddish yellow to yellow brown (7.5YR5/8–10YR5/8). Posterior underparts of the nominate form are pale olive yellow to yellow ochre (2.5Y7/7–10YR7/6); posterior underparts of zimmeri are light reddish yellow brown to brownish yellow (7.5YR6/8–10YR6/8).

Distribution. South of the Rio Amazonas (Solimões) and Rio Napo, Brazil, Ecuador, and Peru; east of the Andes in Ecuador, Peru, and Bolivia; and west of the Rio Madeira and Rio Beni in Brazil and Bolivia.

Remarks. Chapman (1925) described M. l. zimmeri as a subspecies distinct from nominate longipennis and M. l. paraensis , but he did not have specimens of M. l. garbei for comparison. Although in comparisons of vocalizations we found no diagnostic differences between zimmeri and garbei , females of available specimens of zimmeri and garbei differed in coloration.An mtDNA genetic distance (~0.6%) between them suggests that they may be evolving independently, but our only tissue samples of zimmeri were from Ecuador, distant from the putative barrier between them. The subspecies M. g. zimmeri should be maintained at least until additional specimens are obtained for plumage comparisons and genetic analysis. If subspecies status is supported, the likely barrier between them is the Rio Marañón, Peru.