Serra Antwren

Antwrens in the genus Formicivora have comparatively long tails, and the males are unusual in having underparts that are darker than the upperparts. The serra antwren is 12 to 14 cm (4.7 to 5.5 in) long and weighs 10 to 13 g (0.35 to 0.46 oz). Adult males of the nominate subspecies F. s. serrana have a white supercilium that extends down the neck, along the side of the breast, and widens and grays on the flanks. Their crown and upperparts are rufous-brown with white edges on the outer scapulars and a hidden white patch between them. Voice: The vocalizations of the three subspecies of serra antwren differ little. Their song is a "monotonous series of dry chup notes at same pitch and pace" that may be sung as many as 50 times in succession though sometimes with short pauses. They also make a "short downslurred nasal whine...up to 20 notes" and a "high-pitched squeaky disyllabic kee-ip note...