Rondine dorata

Identificazione

A small swallow, the golden swallow measures, on average, 12 cm (4.7 in). The adult of the nominate subspecies' upperparts, including the sides of the head, the cheek, and the chin, are an iridescent bronze. The ear coverts and lores are duller, and the forehead, crown, and nape are more green. This contrasts with the golden or coppery-bronze colouring of the mantle, shoulders, back, rump, and uppertail-coverts. The lesser and median-coverts are more coppery, with the greater and primary wing-coverts being more green and dusky. The edges of the greater coverts and tertials are more golden. The primaries, secondaries, tail, axillaries, and underwing-coverts are dusky bronze-green, with the axillaries and underwing-coverts having this colour only on the edges. The tail is only slightly forked on the nominate subspecies, unlike the more deeply forked tail of the other subspecies, sclateri. Its underparts are white, with dusky bronze streaks on the flanks. The legs and the feet are dark brown and the bill is black. Its irides are also dark brown. The female is similar, although some of the underparts, specifically the breast and occasionally the throat and undertail-coverts, are mottled grey-brown. The mottling around the breast and collar is likely to decrease over time. The juvenile, like the female, is mottled grey-brown. The juvenile also has less glossy plumage and the sides of its head are a dusky grey.<p>The other subspecies, sclateri, has slightly longer wings and a smaller bill. The plumage is less golden, with the forehead and uppertail-coverts being blue-green, and with both the wings and tail being blue-black. The underparts of T. e. sclateri also vary in being pure white without streaks.<p>This bird has a soft, two-note call, often described as a tchee-weet, that is repeated.

Tassonomia

The golden swallow was first described as Hirundo euchrysea by English naturalist Henry Gosse, in his 1847 book The Birds of Jamaica, many years after European settlement of the island. Early naturalists were not aware of this species. The current genus Tachycineta, on the other hand, was originally described in 1850 by the ornithologist Jean Cabanis. The binomial name is from Ancient Greek. Tachycineta is from takhukinetos, "moving quickly", and the specific euchrysea is from eukhrusos, meaning "rich in gold". This is derived from eu, meaning "plenty", and khruseios, meaning "golden".<p>This species has two subspecies; the second, Tachycineta euchrysea sclateri, was originally suspected of being a distinct species by Henry Bryant in 1866, who recorded it as "var. dominicensis?" and noted differences in plumage from the nominate subspecies in Jamaica. However, his report lacked a species description. It was finally described as Hirundo sclateri in 1884 by American ornithologist Charles Cory, who felt it distinct enough to warrant separate species status. The subspecies name sclateri is dedicated to Philip Sclater, an English zoologist. The nominate subspecies, T. e. euchrysea, is extinct.<p>This swallow, along with the violet-green swallow and Bahama swallow, comprise a clade. It is also considered to be of the subgenus Tachycineta, the nominate subgenus, in addition to the violet-green swallow, Bahama swallow, and tree swallow.

Nome scientifico

Tachycineta euchrysea

Autorità

(Gosse, 1847)

Ordine

Passeriformi

Famiglia

Hirundinidae

Genere

Tachycineta

Areale e habitat

The golden swallow is native to the island of Hispaniola, and formerly Jamaica. The subspecies that resided in Jamaica, Tachycineta euchrysea euchrysea, is extinct. It was found up to elevations of 2,000 m (6,600 ft), from sea level on Jamaica, and currently found from 800 m (2,600 ft) on Hispaniola. It is likely that this species, when not breeding, moves down to lower altitudes. The estimated extent of occurrence for this swallow is 8,100 km2 (3,100 sq mi). Primarily inhabiting hills of the interior of islands, this swallow prefers open country, but will occasionally be seen in forests and over towns. It is restricted to patches of montane forest that consist primarily of Hispaniolan pine. Never common in Jamaica, it was restricted to mountainous limestone country in the island's interior.

Migrazione

Resident species

Comportamento

The golden swallow usually builds its deep cup nest in dead snags, especially those of the Hispaniolan pine, in holes created by woodpeckers, primarily the Hispaniolan woodpecker. It also nests in caves, under the eaves of houses, and in recently burned stands. The nests are made with fine vegetable fibres like silk, cotton, and pappus, with the seeds being broken off from the fibres. The nests are lined with cotton, silk, and feathers. One nest had a diameter of about 12 cm (4.7 in), and a depth of about 5 cm (2.0 in).<p>The breeding season occurred from June to July in Jamaica, and occurs from April to July in Hispaniola. When breeding, the golden swallow usually nests in pairs and occasionally will nest in colonies. This swallow is not known to compete for nests with any other birds. The only species, an insect, that is known to inhabit nest boxes occupied by golden swallows is Polyancistrus loripes, a species of katydid. Only about 9.6% of nesting attempts are second nesting attempts, although this number may be low.<p>The clutch of this swallow is two to four white to creamy white eggs with little spotting. The eggs measure around 18.4 mm × 13.1 mm (0.72 in × 0.52 in), and weigh 1.7 g (0.060 oz) on average. They are generally laid one per day, although there are instances of the female skipping a day in laying. The incubation period ranges from 17 to 20 days, with the female incubating the young. The young usually fledge 24 to 27 days after they hatch.<p>This species is an aerial insectivore, usually feeding on flies, Hemiptera (or true bugs), and various other insects. It usually can be seen to forage low to the ground, either by itself or in small groups. It is not usually found to forage above 20 m (66 ft), and very rarely above 30 m (98 ft). Black swifts flying below 20 m (66 ft) are frequently found near golden swallows when the swallows are foraging. It is known to forage in most habitats except the forest. Generally, the golden swallow starts to forage at dawn, with activity increasing in the morning and decreasing during the afternoon.

Conservazione

Tendenza della popolazione

declining