Bruant à sourcils jaunes

En bref

  • Scientific Name: Ammodramus aurifrons
  • Spanish Name: Chingolo de Cejas Amarillas
  • Family: Passerellidae
  • Known Nicknames: Yellow-browed Sparrow, Yellow-browed Grass Finch
  • Average Length: 12–13 cm / 4.7–5.1 in
  • Average Weight: 14–20 g / 0.5–0.7 oz
  • Wingspan: 18–20 cm / 7–8 in
  • Key Feature: Prominent yellow supercilium (eyebrow) contrasting with gray head
  • Primary Diet: Granivore (seeds), with some insects
  • Range: Northern South America (Colombia, Venezuela, Ecuador, Peru, Bolivia, Brazil, Guyana, Suriname, French Guiana)
  • Habitat: Open grasslands, savannas, agricultural fields, and wet meadows
  • Social Structure: Small flocks, often in pairs or family groups
  • Nesting/Breeding: Cup-shaped nest on the ground, usually hidden in grass tussocks
  • Statut de conservation : Préoccupation mineure (LC)
  • Évolution démographique : Stable

The Yellow-browed Sparrow (*Ammodramus aurifrons*) is a small, secretive songbird native to the grasslands and agricultural fields of central South America, distinguished by its most striking feature: a vivid, golden-yellow stripe above the eye that contrasts sharply with its otherwise drab, streaked brown plumage. This sparrow has a stout, conical bill ideal for cracking seeds, and its back and wings are patterned with dark streaks and chestnut tones, providing excellent camouflage among tall grasses. A special behavioral trait is its distinctive, insect-like song—a thin, buzzing trill that rises in pitch—often delivered from a low perch or during a fluttering display flight. Despite its bright brow, it is more often heard than seen, as it skulks through dense vegetation, making it a prized find for birdwatchers exploring the pampas.

Faits amusants

The Yellow-browed Sparrow is a master of disguise, using its namesake bright yellow eyebrow stripe not for show, but as a disruptive camouflage pattern that breaks up its outline against the dappled light of the forest floor. A quirky behavior is its “foot-trembling” foraging technique, where it rapidly vibrates one foot against the leaf litter to startle hidden insects into moving, allowing it to snatch them mid-flight. It also has an unusual social habit of joining mixed-species flocks led by antbirds, following army ant swarms not for the ants themselves, but to feast on the fleeing invertebrates they flush out.

Habitats et répartition

The Yellow-browed Sparrow inhabits open and semi-open grassy areas, often near water, including savannas, flooded grasslands, marshes, and agricultural fields with scattered bushes or trees. It avoids dense forests, preferring lowland regions with tall grasses and moist soils. Its geographical range extends across northern and central South America, from eastern Colombia and Venezuela through the Guianas, Brazil, and into Bolivia, Paraguay, and northern Argentina. It is also found in parts of Peru and Ecuador, typically below 1,000 meters in elevation, though local populations may occur slightly higher in suitable habitats.

Comportements & Reproduction

The Yellow-browed Sparrow is generally monogamous, with pairs forming during the breeding season, though some males may attempt extra-pair copulations. Socially, they are loosely colonial during nesting, often building cup-shaped nests in low shrubs or grass tussocks within close proximity to one another, which may provide some collective vigilance against predators. A unique reproductive strategy involves the female laying a second clutch in a separate nest while the male continues to feed the first brood, effectively allowing double brooding within a single season. The male also assists in incubating the eggs, and both parents feed the chicks, which fledge after about 10–12 days.

Alimentation

The Yellow-browed Sparrow (*Ammodramus aurifrons*) is primarily a granivore, with seeds, particularly those of grasses and sedges, forming the bulk of its diet throughout the year. It forages on the ground, often in small flocks, meticulously picking seeds from the soil surface or directly from low-growing plants. An interesting facet of its feeding behavior is its strong seasonal shift; during the breeding season, it incorporates a significant amount of animal matter, actively hunting small insects, spiders, and other invertebrates to provide essential protein for its rapidly growing chicks. This dietary flexibility allows it to thrive in its native grasslands and savannas, and it has been observed occasionally feeding on fallen grain in agricultural fields, showcasing its adaptability to human-altered landscapes.

Couleurs

The Yellow-browed Sparrow has a pale grayish-brown body with fine dark streaking on the back and wings, but its most distinctive feature is a bright yellow stripe above the eye (the "eyebrow") and a yellow patch on the throat. Its underparts are buffy-white, and it lacks bold wing bars or facial patterns, providing effective camouflage in dry grasslands and scrub.