Thrasher, White-breasted

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Thrasher, white-breasted

Ramphocinclus brachyurus

phylum: Chordata

class: Aves

order: Passeriformes

family: Mimidae

status: Endangered, IUCN Endangered, ESA

range: Martinique, Saint Lucia

Description and biology

An average white-breasted thrasher measures 9 to 9.5 inches (23 to 24 centimeters) long. The color of the plumage (covering of feathers) on the majority of the bird's body is dark brown. The side of its head is black, and its underparts are strikingly white.

This thrasher often gathers in single pairs or in small flocks of four or five pairs. It feeds by foraging on the ground for insects, seeds, and berries. The white-breasted thrasher is very territorial: when threatened, it will cock its tail and chatter like a wren. (Thrashers tend to sing in short, musical sounds. Birds like wrens often make scolding, chattering sounds.)

Breeding season appears to take place between April and July. The female white-breasted thrasher lays a clutch (eggs

produced at one time) of 2 greenish-blue eggs in a bulky nest made of twigs and leaves. Based on related species, biologists (people who study living organisms) estimate that it probably takes 12 to 13 days for the eggs to hatch. The nest is often found 7 to 20 feet (2 to 6 meters) above ground in young trees.

The white-breasted thrasher species is divided biologically into two subspecies: Ramphocinclus brachyurus brachyurus and Ramphocinclus brachyurus santaeluciae. The main physical difference between the two is color. The birds of the subspecies brachyurus are lighter than those of the subspecies santaeluciae.

Habitat and current distribution

The white-breasted thrasher is unique to the Caribbean islands of Martinique and Saint Lucia. Martinique is home to the thrasher subspecies brachyurus. Biologists estimate that between 15 and 40 pairs of these birds currently exist. On Saint Lucia, home to the thrasher subspecies santaeluciae, fewer than 50 pairs of birds exist.

White-breasted thrashers prefer to inhabit dense thickets in semi-arid (partly or mostly dry) woodland. Those thrashers on Martinique have also been found to inhabit deep woods and areas bordering streams. On Saint Lucia, some thrashers have been observed inhabiting deciduous (shedding) trees ranging in height from 10 to 70 feet (3 to 21 meters).

History and conservation measures

The white-breasted thrasher is one of the rarest birds of the West Indies. Although considered quite common on Martinique in the nineteenth century, the bird was considered extinct there by 1950. That same year, it was rediscovered on the Presqu'île de la Caravelle, a peninsula that juts 5 miles (8 kilometers) out from the island into the Atlantic Ocean.

On Saint Lucia, the thrasher was also considered common and widespread during the nineteenth century. By the 1930s, however, it was extinct in some areas and rare in others on the island.

Habitat destruction on both Martinique and Saint Lucia has been, and continues to be, one of the major threats to the white-breasted thrasher. The bird is also threatened by introduced predators such as mongooses and rats. The white- breasted thrasher is easy prey for these animals because it spends much time feeding on the ground and it is not a strong flier.

On Martinique, the white-breasted thrasher's range lies within the Caravell Natural Reserve. On Saint Lucia, part of it lies within the Castries Forest Reserve.