Wedge-tailed Grass-Finch
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Quick Facts
- Scientific Name: Emberizoides herbicola
- Spanish Name: Semillero colicuña
- Family: Thraupidae
- Known Nicknames: Wedge-tailed Finch, Wedge-tailed Grass Finch
- Average Length: 18–20 cm / 7–8 in
- Average Weight: 25–35 g / 0.9–1.2 oz
- Wingspan: 25–30 cm / 10–12 in
- Key Feature: Long, pointed, wedge-shaped tail with white outer feathers
- Primary Diet: Granivore (seeds), also insects
- Range: Central and South America, from Costa Rica to northern Argentina
- Habitat: Open grasslands, savannas, and cerrado with scattered bushes
- Social Structure: Solitary or in pairs, occasionally in small groups
- Nesting/Breeding: Cup-shaped nest built low in grass or shrubs
- Conservation Status: Least Concern (LC)
- Population Trend: Stable
The Wedge-tailed Grass-Finch (*Emberizoides herbicola*) is a striking inhabitant of South American grasslands, named for its most distinctive feature: a long, sharply pointed tail that resembles a wedge, aiding in agile maneuvering through dense grasses. Its general appearance is subtly elegant, with olive-brown upperparts streaked with black, a pale yellowish underbelly, and a conspicuous white eyebrow stripe that gives it an alert, inquisitive expression. A special feature of this finch is its vibrant, melodic song—a series of clear, whistled notes often delivered from a prominent perch—which serves as both a territorial declaration and a key identifier in its open savanna habitat. Adaptable yet specialized, it forages low to the ground for seeds and insects, its wedge-tail acting as a natural rudder as it flits between grass stalks.
Fun Facts
Despite its name, the Wedge-tailed Grass-Finch is not a true finch but a member of the tanager family, a quirky taxonomic twist. It has a peculiar habit of "anting," where it deliberately rubs ants on its feathers to use the formic acid as a natural insecticide and feather conditioner. Its wedge-shaped tail is an adaptation for rapid, agile flight through dense grasses, allowing it to escape predators by diving into thick vegetation. Males perform a bizarre, bouncing display flight, singing while hopping vertically into the air like a tiny, feathered pogo stick to attract mates.
Habitats & Distribution
The Wedge-tailed Grass-Finch inhabits open, grassy environments such as savannas, dry grasslands, and shrubby pastures, often in regions with scattered bushes and termite mounds. It is typically found in lowland areas and avoids dense forests or humid rainforests. Its geographical range extends across central and eastern South America, from northeastern Brazil and the Guianas south through central Bolivia, Paraguay, and into northern Argentina and Uruguay. The species also occurs in the Cerrado and Pantanal ecoregions, as well as in the Gran Chaco, where it favors seasonally dry or fire-maintained grasslands.
Behaviours & Reproduction
The Wedge-tailed Grass-Finch is typically monogamous, with pairs forming during the breeding season and defending a small territory within their grassland habitat. Males perform a song flight, rising into the air with a fluttering display to attract a mate and ward off rivals. The social structure outside of breeding is loose, with small, non-competitive flocks foraging together. A unique reproductive strategy involves building a domed nest with a side entrance, often woven into dense grass tussocks near the ground, which provides camouflage and protection from predators. The female incubates the clutch of two to three eggs alone, but both parents feed the chicks, and they may raise two broods in a single season if conditions are favorable.
Diet
The Wedge-tailed Grass-Finch is primarily a granivore, with its diet consisting almost entirely of grass seeds, particularly those from the Poaceae family, which it forages for on the ground by pecking at the soil and low vegetation. An interesting fact about its feeding behavior is that it often forages in small flocks, and during the dry season when seeds become scarce, it will supplement its diet with small insects, such as beetles and caterpillars, to meet its protein needs. Additionally, this finch has a specially adapted, stout bill that is perfectly shaped for cracking open tough seed husks, allowing it to exploit hard-coated seeds that other birds might avoid.
Colors
The Wedge-tailed Grass-Finch has an olive-brown back with dark streaking, a pale yellow throat and belly, and a distinctive bright yellow rump visible in flight. Its long, pointed tail feathers are dark with white outer edges, and the face shows a subtle yellow supercilium. This plumage provides effective camouflage among dry grasses, with the streaked upperparts breaking up its outline against the vegetation.
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