About Microcerculus marginatus (P.L.Sclater, 1855)
The southern nightingale-wren (Microcerculus marginatus) has a scientific name first described by P. L. Sclater in 1855. Adults of this species measure 11 cm (4.3 in) in total length. Males weigh between 18.2 and 22 g (0.64 to 0.78 oz), while females weigh between 17 and 18 g (0.60 to 0.63 oz). For the nominate subspecies, adults have a dull gray-brown face, a deep chocolate-brown crown and upperparts with a reddish tinge on the rump, and a very short dark chocolate tail. Their chin, chest, and upper belly are white, with some black scalloping along the sides of the chest. The lower flanks and lower belly are dark chocolate. Juveniles resemble adult nominate subspecies, but also have darkish barring on the crown and back, and dark brown feather tips on the underside. Each recognized subspecies has distinct plumage or physical traits: M. m. squamulatus is similar to the nominate but has scaly markings on its underparts; M. m. taeniatus also has scaly underparts, plus a more extensive reddish tinge on the upperparts and blackish barring below; M. m. corrasus is similar to the nominate, but has purer white underparts with narrow dark bars; M. m. occidentalis has a longer and thinner bill, darker upperparts and flanks, and broad dark bars on the abdomen; M. m. luscinia has a pale gray throat that becomes brownish gray on the breast and belly. Each subspecies also has a separate geographic range: M. m. luscinia ranges from central Costa Rica to eastern Panama's Darién Province; M. m. corrasus is found in the Santa Marta region of northern Colombia; M. m. squamulatus occurs across northern Colombia outside the Santa Marta region, extending into northern Venezuela; M. m. occidentalis lives in western Colombia and northwestern Ecuador; M. m. taeniatus is found in western Ecuador; M. m. marginatus (the nominate subspecies) occurs throughout Amazonia, spanning from Venezuela, Ecuador, Colombia, Peru, and Bolivia to near the mouth of the Amazon River in Brazil. The southern nightingale-wren inhabits the lower levels of dense humid tropical forest. Its documented elevation range reaches 1,700 m (5,600 ft) in Costa Rica, 1,400 m (4,600 ft) in Colombia, and 1,800 m (5,900 ft) in Venezuela. There is also a single documented record of the species from Panama at 3,100 m (10,200 ft).
