The tropical gnatcatcher (Polioptila plumbea) is a small active insectivorous songbird, which is a resident species throughout a large part of northern South America. It was formerly considered as conspecific with the white-browed gnatcatcher.
Taxonomy
The tropical gnatcatcher was formally described in 1788 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it in the genus Todus, coined the binomial name Todus plumbeus and specified the type locality as Suriname in South America. The specific epithet plumbeus is Latin meaning "plumbeous" or "lead-coloured". Gmelin based his account on the "Plumbeous tody" that had been described in 1782 by the English ornithologist John Latham in his book A General Synopsis of Birds. Latham had examined a specimen in the collection of the British Museum. The tropical gnatcatcher is now one of 17 gnatcatchers placed in the genus Polioptila that was introduced in 1855 by the English zoologist Philip Sclater.
The tropical gnatcatcher was formerly considered to conspecific with the white-browed gnatcatcher (Polioptila bilineata). The species were split based on a phylogenetic study of the gnatcatchers published in 2018.
Seven subspecies are recognised: P. p. maior Hellmayr, 1900 – north Peru P. p. anteocularis Hellmayr, 1900 – central Colombia P. p. plumbiceps Lawrence, 1865 – northeast, east Colombia and north Venezuela P. p. innotata Hellmayr, 1901 – east Colombia to central Guyana and north Brazil P. p. plumbea (Gmelin, JF, 1788) – Suriname, French Guiana and north Brazil P. p. atricapilla (Swainson, 1831) – northeast Brazil P. p. parvirostris Sharpe, 1885 – east Ecuador, northeast Peru and northwest Brazil
Description
The adult tropical gnatcatcher is long, and weighs . Its "jizz" is similar to that of other gnatcatchers; a small bird with a relatively long thin bill, a long frequently cocked tail, grey upperparts and whitish underparts. The central rectrices are black, while the outer are white (consequently, the tail appears primarily black from above, white from below), and there is a white patch in the wing (caused by broad white edging to the tertials). Males of the nominate group have a contrasting black cap that reaches just below the eye, while this is lacking in females, which instead have a grey cap (same colour as back). Some females have an irregular black post-ocular patch. This is especially prominent in female of the subspecies atricapilla from north-eastern Brazil.
Males of the white-browed gnatcatcher (bilineata group) resemble males of the nominate group, but the white of their underparts extends clearly above the eye, resulting in a more restricted black cap, which, however, often is connected with a fine black line from the nape to the rear of the eye. Females resemble males, but with the black of the cap replaced by grey, except for an irregular black patch in the post-ocular region (lacking in some females). As the white in both sexes extends above the eye, they appear rather "white-browed" (unlike the nominate group), resulting in the common name proposed for this group if considered a separate species.
The final group, which only includes the taxon maior (the so-called Marañón gnatcatcher), is distinctive. Males resemble males of the nominate group, but, except for their white forecrown, females resemble males of the bilineata group. Juveniles of all groups resemble females.
The tropical gnatcatcher has a thin buzzy gezzz call and a trilled swee see see si si si su su song. However, exact structure and tone of the voice varies greatly over its range.
Distribution and ecology
The nominate group if found from north-eastern Brazil (the Caatinga region), west through the Amazon Basin, and north to the Guianas, northern Venezuela and northern Colombia (including the valleys of Magdalena and Cauca). The bilineata group is found from north-western Peru, through the Chocó and Central America, to southern Mexico. The Marañón gnatcatcher is restricted to the Marañón valley in northern Peru.
Both the nominate and the bilineata group are found in a wide range of wooded habitats, ranging from the arid woodland and scrub (such as the Caatinga in Brazil) to humid forest (such as the various types of humid forest in the Amazon). They are mainly found in lowlands below an altitude of , but the taxon maior, which is restricted to dry woodland and scrub, is found at altitudes of .