Averla formichiera maggiore

Identificazione

The great antshrike is a large and distinctive bird, 19 to 20 cm (7.5 to 7.9 in) long and weighing 47.5 to 70 g (1.7 to 2.5 oz). The species exhibits significant sexual dimorphism, though both sexes of all subspecies have a large crest, a red iris, and a heavy black bill with a hook at the end like true shrikes. Adult males of the nominate subspecies T. m. major have a black head with the color extending to below the eye. Their upperparts are mostly black with a usually hidden white patch between the scapulars. Their wings are black with large white spots on the coverts that appear as bars when perched and white edges on the primaries. Their tail is black with white spots on the outer feathers. Their throat, chin, and the rest of their underparts are white with a gray tinge on the flanks. Adult females have a rufous crown and browner lores and ear coverts. Their upperparts are reddish yellow-brown, their wings reddish yellow-brown with paler feather edges, and their tail is rufous. Their chin, throat, and center of their breast are white; their crissum is light cinnamon, and the rest of their underparts are white with a cinnamon tinge. Juveniles have cinnamon or buff barring on their upper- and underparts that remains fainly in subadults.<p>The other subspecies of the great antshrike differ from the nominate and each other thus:

Tassonomia

The great antshrike was described by the French ornithologist Louis Pierre Vieillot in 1816 and given the binomial name Thamnophilus major. The current genus Taraba was introduced by the French naturalist René Lesson in 1831. <p>The great antshrike has these ten subspecies:<p>The great antshrike is the only member of genus Taraba. Its closest relatives appear to be the fasciated and bamboo antshrikes of genus Cymbilaimus. The subspecies' vocalizations fall into two groups, T. m. melanocrissus through T. m. granadensis and T. m. semifasciatus through T. m. major. The first, found in Central America and mostly west of the Andes, may represent a separate species from the other, which are found east of the Andes. In addition, differences within the members of each group may not be significant enough in some cases to warrant subspecies status.

Nome scientifico

Taraba major

Autorità

(Vieillot, 1816)

Ordine

Passeriformi

Famiglia

Thamnophilidae

Genere

Taraba

Areale e habitat

The subspecies of the great antshrike are distributed thus:<p>The South American Classification Committee of the American Ornithological Society has records of vagrant individuals in Uruguay.<p>The great antshrike inhabits a wide range of semi-humid to humid tropical zone landscapes, favoring in most of them areas of dense understorey vegetation. On the Pacific slope it does extend somewhat into the subtropical zone. The landscapes include gallery forest, savanna woodlands, younger secondary forest, the edges and clearings of evergreen forest, river islands, and locally drier but not arid areas. It is often associated with stands of bamboo. The exception to these general habitats is subspecies T. m. stagurus, which occurs in deciduous forest and taller parts of the caatinga. In elevation it occurs below 1,000 m (3,300 ft) in much of its range, but reaching 1,100 m (3,600 ft) in Costa Rica, 1,400 m (4,600 ft) in Colombia, 1,500 m (4,900 ft) in Peru, and 2,200 m (7,200 ft) in Venezuela. It seldom exceeds 750 m (2,500 ft) in northern Central America.

Migrazione

Resident species

Comportamento

The great antshrike is presumed to be a year-round resident in most of its range though some seasonal movements are suspected in Argentina.<p>The great antshrike feeds on a wide variety of largish insects and other arthropods, small molluscs, small vertebrates including mammals, lizards, and minnows, and a small amount of vegetable matter. Its diet appears to vary considerably across its range. It forages singly or in pairs, almost always within about 5 m (15 ft) of the ground in heavy cover. It hops sluggishly from branch to branch, gleaning prey from leaves, stems, and branches by reaching and sometimes jumping from a perch. It often drops to the ground to seize prey. In the Brazilian Pantanal it has been observed feeding on aquatic prey while standing on water hyacinths. It sometimes joins mixed-species feeding flocks (though almost never does so in Venezuela) and occasionally follows army ant swarms./<p>The great antshrike's breeding season varies geographically, spanning April to July in Costa Rica, March to July in Trinidad, January to June in Suriname, January to April in northeastern Brazil, and October to December in Argentina. Its nest is a cup made from a variety of plant fibers whose composition varies by habitat. It is typically suspended by its rim in a branch fork or between two branches and usually within about 3 m (10 ft) of the ground. The clutch is usually two or three eggs; three are more common in the southern part of the species' range. The eggs' color and pattern vary geographically though generally they have a creamy white to pale buff base. Both sexes incubate the clutch during the day and the female alone at night. In Costa Rica the incubation period is 17 to 18 days and fledging occurs 12 to 13 days after hatch. These periods elsewhere and other details of parental care are not known. Shiny cowbirds (Molothrus bonariensis) are frequent nest parasites in Argentina.<p>The great antshrike's song is generally "a long, accelerating series of c. 40 notes, 5–14 seconds, usually ending in a snarl", though the more northern and western subspecies tend to sing fewer notes and often omit the snarl. Its calls also vary geographically and include a "long decelerating rattle sometimes ending with a distinct note, shorter rattles often repeated rapidly, a decelerating rolling series of whistles, evenly paced series of harsh notes and of more musical notes, downslurred growl, and somewhat clear, high-pitched whine". Because the species favors dense understorey, it is more often heard than seen.

Conservazione

Tendenza della popolazione

declining