Wedge-tailed Grass Finch

This is a slender, elegant passerine bird characterized by its extraordinarily long, graduated, and wedge-shaped tail, which makes up nearly half of its total length of 20 to 22 centimeters. Its upperparts are heavily streaked with olive-brown and blackish, which provides excellent camouflage within its grassy environment, while its underparts are clean whitish transitioning to pale buff on the flanks and undertail coverts. A key diagnostic feature is its striking bill, featuring a bright yellow mandible contrasted against a dark black culmen. Additionally, it has a subtle whitish supercilium and a thin, pale eyering that outlines its face.

Geographical distribution It exhibits a highly disjunct distribution across Central and South America. Populations can be found in the savannas of southwestern Costa Rica and Panama, extending through northern South America in Colombia, Venezuela, and the Guianas. It is widely distributed across central and southern Brazil (primarily the Cerrado biome), eastern Bolivia, Paraguay, and reaching its southernmost limit in northeastern Argentina.

Habitat: It strictly frequents open formations, primarily inhabiting tall-grass savannas, pristine grasslands, shrubby pastures, and damp grassy plains near wetlands. It prefers undisturbed native grasslands where high grass cover is abundant, ranging from sea level up to elevations of approximately 1500 meters.

Feeding Its diet is omnivorous, consisting heavily of grass seeds that are gleaned from the ground or stripped directly from dry seed heads. This granivorous base is supplemented with animal protein, particularly during the breeding season, when it actively hunts for small insects such as grasshoppers, beetles, and small larvae found within the lower vegetative strata.

Behavior: It is a predominantly terrestrial and secretive species, usually observed singly or in pairs. Although it spends most of its time foraging quietly on the ground or within dense grass, males become highly visible during the breeding season when they perch on top of tall stalks or low bushes to sing. Its song consists of a sequence of metallic, sweet, and rising whistles. The flight pattern is jerky and low, with its long tail conspicuously pumping up and down as it moves between perches.

Nesting This species breeds during the regional rainy seasons when food resources are most abundant. It builds a cup-shaped nest constructed from dry grass blades and fine fibers, which is carefully hidden low to the ground, usually tucked inside a dense grass tussock. The clutch size typically consists of 2 to 3 white eggs speckled with dark brown or black markings on the larger end, which are incubated primarily by the female.

Conservation status It is currently listed as Least Concern (LC) on the IUCN Red List of Threatened Species. While the conversion of native grasslands into intensive monocultures and pastures poses localized threats, its vast geographical distribution and ability to tolerate moderately degraded open habitats keep its global population stable.