Red-billed streamertail

The red-billed streamertail (Trochilus polytmus), also known as the doctor bird, scissor-tail or scissors tail hummingbird, is a species of hummingbird in the "emeralds", tribe Trochilini of subfamily Trochilinae. It is endemic to Jamaica and is the national bird of the country.

Taxonomy and systematics
The red-billed streamertail was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae under the binomial name Trochilus polytmus. Linnaeus quoted the description in Latin by the Irish physician Patrick Browne in his The Civil and Natural History of Jamaica which had been published two years earlier in 1756. The specific epithet polytmus is from the Ancient Greek polutimos meaning "costly" or "valuable".

The International Ornithological Committee (IOC), BirdLife International's Handbook of the Birds of the World, and the Clements taxonomy treat the red-billed streamertail and black-billed streamertail (T. scitulus) as separate species. However, the North American Classification Committee of the American Ornithological Society calls T. polytmus "streamertail" and assign the red-billed and black-billed forms to it as subspecies. The two species (or subspecies) interbreed in their narrow contact zone.

The species as defined by the IOC is monotypic: no subspecies are recognised.

Description
The male red-billed streamertail is 22 to 25 cm long including the 10 to 13 cm tail streamers and weighs 4.0 to 6.5 g. The female is about 10.5 cm long and weighs 3.0 to 6.1 g. The adult male has a coral red bill with a black tip. It has a dull black to blue-black crown; it and the nape form a deep velvety black crest. The rest of its upperparts are bright metallic green. Its tail is black with a green to bronzy green gloss. The next to outermost pair of tail feathers is very long, giving the species its English name. The male's face and most of its underparts are metallic yellowish green; the undertail coverts are blue-black or black with a bluish gloss. The adult female's bill is a duller red than the male's. Its upperparts are metallic bronze green to greenish bronze that is duller on the crown. Its tail lacks the male's streamers. Its central pair of feathers are bright bronze green and the rest black with some bronze green gloss, and the outermost two pairs have wide white tips. Its underparts are white with metallic bronze green spots on the breast and flanks. Immature males are similar to the adult but lack the tail streamers; its tail feathers have bronze green tips.

Distribution and habitat
The red-billed streamertail is found throughout Jamaica except in the extreme eastern end, where the black-billed is found. It inhabits evergreen montane forest, lowland tropical forest, and secondary forest. It shuns mangroves and arid highlands. In elevation it ranges from sea level to 1500 m; it is considered fairly common in the lowlands and abundant at middle and higher elevations.

Movement
The red-billed streamertail is an elevational migrant.

Feeding
The red-billed streamertail forages for nectar at a wide variety of native and introduced flowering species; it especially prefers Besleria lutea. It forages at all heights from the ground to the canopy. It has also been observed "robbing" nectar from holes in flowers created by bananaquits (Coereba flaveola) and visiting wells drilled by yellow-bellied sapsuckers (Sphyrapicus varius). In addition to nectar it feeds on small insects taken while hovering or gleaned from foliage or spiderweb.

Breeding
Both sexes of the red-billed streamertail aggressively defend territories. Males court females that enter their territory. Both sexes perch and repeatedly nod their heads, after which the male flies up and down in front of the female while spreading its tail streamers. The species breeds at any time of year, mostly between January and May, and may raise three broods in a year. The nest is a cup of fine plant fibers bound with spiderweb with lichen on the outside. It is typically built on a fine twig between 1 and 3 m above the ground. The female incubates the clutch of two eggs for 17 to 19 days and fledging occurs 19 to 24 days after hatch.

Vocal and non-vocal sounds
The red-billed streamertail's vocalizations include "a loud metallic ting or teet and a prolonged twink-twink-twink dropping in pitch at the end." Adult males in flight produce a distinctive whirring sound. The whirring is synchronized with the wingbeats and video footage shows primary feather eight (P8) bending with each downstroke, creating a gap that produces the fluttering sound.

Status
The IUCN has assessed the red-billed streamertail as being of Least Concern. It has a very large range but its population size and trend are not known. No immediate threats have been identified. "The ready occupation of man-made habitats suggests that habitat loss is unlikely to be a problem."