Grasshopper Sparrow

Identificazione

These small sparrows measure 10–14 cm (3.9–5.5 in) in length, span about 17.5 cm (6.9 in) across the wings and weigh from 13.8 to 28.4 g (0.49 to 1.00 oz), with an average of 17 g (0.60 oz). Adults have upper parts streaked with brown, grey, black and white; they have a light brown breast, a white belly and a short brown tail. Their face is light brown with a white eye ring and a dark brown crown with a central narrow light stripe. Adults sport bright yellow feathers at the crook of their underwing, and have a yellow-to-amber patch above their lores. Males and females cannot be distinguished by their plumage, and young birds molt into adult plumage within a few months of fledging.

Tassonomia

The grasshopper sparrow was described in 1713 by English parson and naturalist John Ray based on a specimen collected in Jamaica. It was described again and illustrated in 1725 by the naturalist and collector Hans Sloane. Both authors used the English name "Savanna bird". When the German naturalist Johann Friedrich Gmelin revised and expanded Carl Linnaeus's Systema Naturae in 1789 he included the grasshopper sparrow. He placed it with the finches in the genus Fringilla, coined the binomial name Fringilla savannarum and cited the earlier authors. The grasshopper sparrow is now placed with two other American sparrows in the genus Ammodramus that was introduced by William Swainson in 1827.<p>Twelve subspecies are recognised:

Nome scientifico

Ammodramus savannarum

Autorità

(Gmelin, JF, 1789)

Ordine

Passeriformi

Famiglia

Passerellidae

Genere

Ammodramus

Areale e habitat

Their breeding habitat is open fields and prairie grasslands across southern Canada, the United States, Mexico and Central America, the Caribbean. There is a small endangered population in the Andes of Colombia and (perhaps only formerly) Ecuador. In the central USA, birds are quick to locate newly available habitat, and can be attracted to sites by playing conspecific song. The spatial distribution of territories on the landscape can be clumped with several individuals defending territories near to one another interspersed by large areas of unused and apparently suitable habitat. The reasons for this clumping are elusive; aggregation is not related to group defense against predators or brood parasite, cooperative care, extra-pair matings, or kin selection. Appropriate habitat is strongly influenced by plant structure and precipitation amounts during previous seasons. Grasshopper sparrows avoid woody vegetation, and in the wetter parts of their range, prefer fields that are burned every 2–3 years (which reduces encroachment of trees and shrubs) and seek out areas that are moderately grazed by cattle or bison.

Migrazione

Migratori completi

Comportamento

Comportamento migratorio: Migratori completi.

Conservazione

Tendenza della popolazione: in diminuzione.

Tendenza della popolazione

in diminuzione