Antbirds and gnat-eaters

The antbirds and gnat-eaters, also called ant thrushes, are 244 species of birds that comprise the relatively large family Formicariidae. These birds only occur in Central and South America, mostly in lowland tropical forests.

The antbirds and gnat-eaters are variable in their body form and size. Their body length ranges from 4–14 in (10–36 cm), and they have short, rounded wings, and a rounded tail that can be very short or quite long. Most species have a rather large head with a short neck, and the bill is stout and hooked at the tip. Species that live and feed in the forest canopy have a relatively long tail and wings, while those of ground-feeding species are shorter.

The colors of the plumage of most species are rather subdued hues of browns and grays, although there are often bold patterns of white, blue, or black. Males and females of most species have different plumage. These birds generally occur in solitary pairs, which are permanent residents in a defended territory.

Species of antbirds forage widely in the forest floor or canopy for their food of insects, spiders, and other invertebrates. Species of antbirds are prominent members of the local, mixed-species foraging flocks that often occur in their tropical forest habitat. These flocks can contain as many as 50 species, and are thought to be adaptive because they allow better detection of birds of prey.

Despite their name, antbirds rarely eat ants. Antbirds received their common name from the habit of some species of following a column of army-ants as it moves through their tropical forest habitat. These predatory assemblages of social insects disturb many insects as they move along the forest floor. Antbirds and other species of birds often follow these columns to capture insects and other prey that have been disturbed by the army ants. About 27 species of ant-birds have the habit of actively following army ants, while other species do this on a more casual, less focused basis.

Antbirds lay two to three eggs in a cup-shaped nest located in a low tree or on the ground. Both parents share in the incubation of the eggs and the nurturing of the young. Pairs of antbirds are monogamous for life, the partners remaining faithful to one another until death.

Species of antbirds are prominent elements of the avian community of the lowland tropical forests that are their usual habitat. In some cases in Amazonia, as many as 30–40 species of antbirds can occur in the same area, dividing up the habitat into subtly defined niches.

The white-faced ant-catcher (Pithys albifrons ) is an ant-following species of the tropical forests of Amazonian Brazil and Venezuela. The ocellated ant-thrush (Phaenostictus mcclennani ) ranges from Nicaragua to Ecuador. The rufous-capped ant-thrush (Formicarius colma ) forages on the floor of Amazonian forests of Brazil, Venezuela, Ecuador, and Peru.

The precise conservation status of many antbird species is unknown, although the abundance of many species of tropical and semi-tropical birds is declining due to the destruction of their natural forest habitat. Among those antbird species whose status is known, the most critically endangered are four species from Brazil—the Alagoas antwren (Myrmotherula snowi ), the Rio de Janiero antwren (M. fluminensis ), the Rondonia bushbird (Clytoctantes atrogularis ), and the Restinga antwren (Formicivora littoralis ).