The Buff-necked Ibis, *Theristicus caudatus*, is a strikingly handsome wading bird native to the open grasslands and savannas of South America, easily distinguished by its unique, elegant plumage. Its most notable feature is the warm, cinnamon-buff collar that wraps around its neck, contrasting sharply with a dark, sooty-gray body and a long, downward-curving, pale pinkish-orange bill. This ibis also sports a distinctive patch of bare, reddish facial skin and vivid red legs, adding to its colorful profile. A special adaptation is its ability to thrive in arid, terrestrial environments far from water, where it uses its sickle-shaped bill to expertly probe the soil for insects, spiders, and small reptiles, often foraging in small, noisy flocks that call with a resonant, clattering “*ka-ka-ka*.”

Faits amusants

The Buff-necked Ibis is a surprisingly loud and social bird, often gathering in raucous flocks that sound like a mix of honking geese and barking dogs, a noise that can carry for over a mile. It has a quirky habit of tilting its long, down-curved bill sideways to probe into mud and leaf litter for insects and small reptiles, a technique that looks almost comical compared to the straight-ahead stabbing of other ibises. One unique adaptation is its ability to soar on thermal updrafts with its wings held in a shallow V-shape, allowing it to cover vast distances across the South American savanna without flapping. Unlike many water-loving ibises, this species prefers dry grasslands and even agricultural fields, where it will often follow cattle to snatch up flushed grasshoppers and spiders.

Habitats et répartition

The Buff-necked Ibis inhabits a range of open and semi-open environments across central and eastern South America. Its preferred habitats include savannas, grasslands, pastures, agricultural fields, and wetlands, particularly along the edges of marshes, rivers, and lakes. It is also frequently found in the cerrado and pantanal regions, as well as in dry scrublands and lightly wooded areas, always avoiding dense forests. Geographically, its distribution spans from eastern Colombia and Venezuela through the Guianas, across much of Brazil, and south into eastern Bolivia, Paraguay, Uruguay, and northern Argentina.

Comportements & Reproduction

The Buff-necked Ibis is a highly social bird, typically found in small, loose flocks of 4 to 12 individuals that forage together in open grasslands and wetlands. Their social structure is based on stable pair bonds that often persist across multiple breeding seasons. During the breeding season, which varies regionally but generally coincides with the local rainy season, pairs become territorial around their nest site. Courtship involves elaborate mutual displays, including bowing, bill-touching, and synchronized aerial flights where the male and female call in duet. They build a bulky stick nest in a tree fork or on a cliff ledge, often reusing the same site annually. A typical clutch contains 2 to 4 eggs, which both parents incubate for about 28 days. A unique reproductive strategy is their strong fidelity to nesting colonies, sometimes aggregating in loose groups where multiple pairs nest in proximity, providing collective vigilance against predators. Chicks are fed by both parents through regurgitation and fledge after approximately 45 days, but they often remain with the family group for several weeks afterward.

Alimentation

The Buff-necked Ibis has a highly carnivorous diet centered on foraging in shallow wetlands, flooded grasslands, and along muddy riverbanks. It primarily feeds on insects such as grasshoppers, beetles, and caterpillars, but also consumes spiders, snails, earthworms, and small vertebrates like frogs, lizards, and even small snakes. An interesting fact is that this ibis often associates with capybaras and other large mammals, snatching up insects flushed from the vegetation by their movement. Additionally, it uses its long, curved bill to probe deep into mud and soil, and it has been observed following army ant swarms to capture prey fleeing the column.

Couleurs

The Buff-necked Ibis has a pale buff or ochre neck and upper chest, contrasting with a dark greyish-brown body, blackish belly, and grey wings. Its most distinctive feature is a large white patch on the upper wing, visible in flight, along with a long, downcurved reddish-orange bill and bare red facial skin. This coloration provides camouflage in its open grassland and savanna habitats by breaking up its silhouette against the ground and sky.