Appearance

Myrmotherula antwrens are very small thamnophilids. The Leaden Antwren is a member of the group of "gray antwrens", the males of which are predominately gray and the females are predominately buffy brown. The male Leaden is a pale gray antwren with white wingbars; the female is plain, gray above and buff below with weak buff wingbars.

Male Leaden Antwren is closely similar to male of the northern subspecies (pallida) of Gray Antwren (Myrmotherula menetriesii), but there is no overlap in habitat: Leaden Antwren is restricted to forests on large river islands and is not found on the adjacent river banks. Also, male Leaden Antwren has plainer wing coverts (lacking the gray, black and white pattern of male Gray Antwren), and has a white interscapular patch (lacking in Gray). Female Leaden Antwren separable from similar species by habitat, by the white interscapular patch, and by the much stronger, whiter wingbars.

Adult, male: Crown, back and rump medium gray; bases of feathers in the center of the back white, forming a concealed white interscapular patch. Remiges dusky. Wing coverts medium gray, tipped white. Tail gray; usually unmarked, but rarely the undersides of the outermost rectrices narrowly are tipped white. Underparts pale gray, palest on the throat.

Adult, female: Crown, back and rump medium brownish gray or olive gray. Bases of feathers in the center of the back white, forming a concealed white interscapular patch. Remiges olive brown. Wing coverts olive brown, narrowly tipped pale buff or whitish buff. Tail gray or dusky. Sides of the face and neck pale gray. Throat whitish buff. Breast and belly pale buff.

Iris: brown

Bill: black (males) or maxilla black, mandible gray (females)

Tarsi and toes: blue-gray

Data from specimens at the Louisiana State University Museum of Natural Science.

Total length: 9-10 cm (Zimmer and Isler 2003), 9.5-10 cm (Ridgely and Tudor 2009), 10 cm (Schulenberg et al. 2007)

Linear measurements:

Mass: male, 9.3 g (range 8.4-10.5 g, n=13); mean female, mean 9.3 g (range 8.2-10.5, n=12). Data from specimens at the Louisiana State University Museum of Natural Science.