Grive à tête orange

Identification

The orange-headed thrush is 205–235 milliimetres (8.1–9.25 in) long and weighs 47–60 grammes (1.7–2.1 oz). The adult male of the nominate subspecies of this small thrush has an entirely orange head and underparts, uniformly grey upperparts and wings, and white median and undertail coverts. It has a slate-coloured bill and the legs and feet have brown fronts and pink or yellowish rears.<p>The female resembles the male but has browner or more olive upperparts and warm brown wings, but some old females are almost identical to the male. The juvenile is dull brown with buff streaks on its back, and a rufous tone to the head and face; it has grey wings. The bill is brownish horn, and the legs and feet are brown.<p>This species' orange and grey plumage is very distinctive, and it is unlikely to be confused with any other species. Differences between the subspecies, as described above, can be quite striking, as with the strong head pattern on G. c. cyanota, but may be less obvious variations in plumage tone, or whether there is white on the folded wing. As with many other thrushes, all forms of this species shows a distinctive underwing pattern, with a strong white band.<p>Calls of the orange-headed thrush include a soft chuk or tchuk, a screeching teer-teer-teer, and a thin tsee or dzef given in flight. However, this bird is generally silent especially in winter. The song is a loud clear series of variably sweet lilting musical notes, recalling the quality of the common blackbird, but with the more repetitive structure of the song thrush. It also includes imitations of other birds like bulbuls, babblers and common tailorbird. It sings from a perch in a leafy tree, mostly early morning and late afternoon.

Taxonomie

This species was first described by John Latham in 1790 as Turdus citrinus, the species name meaning "citrine" and referencing the colour of the head and underparts. It has about 12 subspecies. Rasmussen and Anderton (2005) suggest that this complex may consist of more than one species.<p>The following table summarises selected physical measurements for those subspecies for which data is available.

Nom scientifique

Geokichla citrina

Autorité

(Latham, 1790)

Ordre

Passériformes

Famille

Turdidae

Genre

Geokichla

Répartition et habitat

The orange-headed thrush breeds in much of the Indian Subcontinent, including Bangladesh, India and Sri Lanka, and through Southeast Asia to Java and southern China. Its habitat is moist broadleaved evergreen woodlands, with a medium-density undergrowth of bushes and ferns, but it also utilises bamboo forests for secondary growth. G. c. cyanota also occurs in large gardens and orchards.<p>This species is often found in damp areas, near streams or in shady ravines. It occurs between 250 and 1830 metres (825– 6040 ft) in the Himalayas and up to about 1500 metres (5000 ft) in Malaysia, Thailand and Java. G. c. aurata is resident between 1000 and 1630 metres (3300–5400 ft) on Mt Kinabalu and Mt Trus Madi, northern Borneo. Some of the subspecies are completely or partially migratory; their wintering habitat is similar to the breeding forests, but more likely to be at lower altitudes.

Migration

Complete migrants

Comportement

The orange-headed thrush is a shy, secretive bird usually occurring alone or in pairs, but is comparatively more easily seen than many other Zoothera thrushes, and several birds may congregate outside the breeding season at a good food source. It has a swift, silent flight, but when disturbed will often sit motionless until the threat has passed.<p>The nest, built by both sexes, is a wide but shallow cup of twigs, bracken and rootlets lined with softer plant material like leaves, moss and conifer needles. It is constructed at a height of up to 4.5 metres (15 ft) in a small tree or bush, with mango trees and coffee bushes being preferred. Three or four, occasionally five, eggs are laid; they are cream or tinted with pale blue, grey or green, and have pale lilac blotches and reddish brown spots. They are incubated for 13–14 days to hatching, with another 12 days until the young birds leave the nest.<p>This species is a host of the pied cuckoo, Clamator jacobinus, a brood parasite which lay a single egg in the nest. Unlike the common cuckoo, neither the hen nor the hatched chick evict the host's eggs, but the host's young often die because they cannot compete successfully with the cuckoo for food. The chestnut-winged cuckoo, Clamator coromandus, and, very rarely, the common cuckoo, Cuculus canorus have also been claimed as parasites on this species.<p>The orange-headed thrush feeds on the ground in dense undergrowth or other thick cover. It is most active at dawn and dusk, probing the leaf litter for insects and their larvae, spiders, other invertebrates and fruit. In Malaysia, wintering birds regularly feed on figs.

Conservation

Tendance de la population

declining