The red-billed scythebill (Campylorhamphus trochilirostris) is a species of bird in the subfamily Dendrocolaptinae of the ovenbird family Furnariidae. It is found in Argentina, Bolivia, Brazil, Colombia, Ecuador, Panama, Paraguay, Peru, and Venezuela.[1]
The red-billed scythebill has these 12 subspecies:[1]
The red-billed scythebill and black-billed scythebill (C. falcularius) have at times been considered conspecific and also as sister species, but genetic data indicate neither is true.[2] The red-billed and curve-billed scythebill (C. procurvoides) have also been suggested as sister species. Some of the subspecies are difficult to distinguish from each other. In addition, a small number of additional subspecies have been suggested to be split from existing ones.[3]
The red-billed scythebill is 22to long and weighs 30to. It is a slim, medium-sized woodcreeper with a very long, slim, dramatically decurved bill. The sexes have the same plumage. Adults of the nominate subspecies C. t. trochilirostris have a thinly streaked face and neck with a weak supercilium. Their crown, nape, and back are reddish olive-brown, with the back being somewhat lighter. Their crown has longish whitish to ochraceous spots with narrow blackish edges; the spots narrow on the nape and become thin streaks on the upper back. Their rump is cinnamon-rufous that contrasts little with the back, their flight feathers are rufous-chestnut, and their tail is a slightly darker rufous-chestnut. Their wing coverts have wide reddish olive-brown edges and the tips of the primaries are dusky. Their throat and chin are white, the latter with thin brownish streaks. Their underparts are a slightly lighter brown than the back; their breast has buff streaks that narrow on the belly but don't continue onto the undertail coverts. Their underwing coverts are light cinnamon to ochraceous. Their iris is dark brown to hazel, their bill bright red or reddish brown (often with a dusky tip and base), and their legs and feet grayish olive to dull pea-green. Juveniles are less richly colored than adults, with less well defined and more ochraceous streaks, and a darker and much shorter bill.[3]
The other subspecies of the red-billed scythebill differ from the nominate and each other thus:[3] [4] [5] [6]
The subspecies of the red-billed scythebill are found thus:[1] [3]
The red-billed scythebill inhabits a wide variety of wooded landscapes, most of which are open to semi-open. These include Gran Chaco woodland, gallery forest, cerrado, caatinga, forest clusters in savannah, secondary forest, and some scrublands. In the Amazon Basin it favors seasonally flooded várzea and igapó forest and riverside canebrakes. In elevation it mostly occurs below about 1200m (3,900feet) but reaches 1900m (6,200feet) in Ecuador and 2100m (6,900feet) in Venezuela.[3] [4] [5] [6]
The red-billed scythebill is believed to be a year-round resident throughout its range.[3]
The red-billed scythebill's diet is chiefly arthropods, especially soft-bodied ones like spiders, and also includes small vertebrates. It usually forages singly, though sometimes in pairs, and often joins mixed-species feeding flocks. It hitches up and along trunks and branches, mostly from the upper level of the understory to the subcanopy but also sometimes higher and lower. It typically takes its prey by probing crevices and holes in bark, bamboo, rotting wood, moss clumps, bromeliads, and epiphytes.[3] [5] [6]
The red-billed scythebill's breeding seasons vary widely across its very large range. For instance, it nests between May and July in northern Venezuela and September to November in southern Brazil. It nests in a cavity in a tree or stump which it lines with leaves and other plant matter. The clutch size is one to three eggs though usually two; the incubation period and time to fledging are not known. Evidence suggests that both parents contribute to caring for the brood.[3]
Like its breeding seasons, the red-billed scythebill's songs vary widely throughout its range. One in Venezuela is "a rapid descending whinny...'we’he’he’he’he’he’he’e’e’e’e’e' ". In western Ecuador and Peru it is "a descending and gradually slowing series of fewer whistled notes, 'tuwee-tuwee-toowa-tew-tew' ".[3] In northeastern Brazil the song is "a short series of fluted notes 'wuut wuut wit-wit-triffit' " that ascends at the end.[4] The species also makes a variety of calls.[3] [4] [6]
The IUCN has assessed the red-billed scythebill as being of Least Concern. It has a very large range and an estimated population of at least 500,000 mature individuals, though the population is believed to be decreasing. No immediate threats have been identified. It is considered uncommon to fairly common, though local, over most of its range. It is scarce in Panama and at upper elevations. "At least some populations [are] believed to be highly sensitive to human disturbance."[3]