Formicariidae – Antthrushes

The Formicariidae (Antthrush) family consists of smallish passerines of subtropical and tropical Central and South America known as formicariids. They are between 10 and 20 cm in length, and are related to the Furnariidae (Ovenbirds) and the Rhinocryptidae (Tapaculos) and a little more distantly to Thamnophilidae (Antbirds), and Conopophagidae (Gnateaters). This family contains 12 species split evenly in two genera.

Molecular phylogenetic studies indicated that the Formicariidae as previously delimited were highly paraphyletic, judging from comparison of several mt and nDNA sequences. The aberrant bar-bellied ‘antpittas’ of the genus Pittasoma, which were formerly placed here, belong to the gnateater family (which initially was also considered part of the Formicariidae); as the gnateaters proper, they are sexually dichromatic. In addition, the true antpittas formerly placed in this family are now found in their own family, the Grallariidae. On the other hand, at least a large proportion of the Rhinocryptidae, including the type genus Rhinocrypta, seem to be closer to the antthrushes, but are still considered a distinct family.

Rufous-capped Antthrush Formicarius colma – ©Dubi Shapiro

They are forest birds that tend to feed on insects at or near the ground since many are specialist ant eaters. Similar in appearance to small rails, their sexes are alike in plumage, which, in most cases, is drab in appearance with shades of (rusty) brown, black, and white being their dominant tones. Compared to other birds that specialise in following ants, this family is the most tied to the ground. The long, powerful legs, which lend the birds a distinctive upright posture, has led to the common name although they are not related to Turdidae (True Thrushes). Their essentially vestigial tail aid this lifestyle.

Short-tailed Antthrush Chamaeza campanisona – ©Dubi Shapiro

Ant-thrushes are indeed vaguely thrush-like in their proportions, but the fact that they generally walk along the forest floor with their tail cocked high over their back weakens the resemblance in life. Their long strides are interspersed by pauses to look about for invertebrate prey, each foot-step being marked by a synchronized pumping of the head and tail. They nest in old tree cavities not too far from the ground, with the loose nest material placed on a floor that is sometimes so deep in rotten wood that it is beneath the surrounding ground surface. They lay two or three eggs, both sexes incubating.

Mayan Antthrush Formicarius moniliger – ©Dubi Shapiro

Like so many forest birds of the Neotropics, they are more often heard than seen, and familiarity with their throaty trilled whistles can be an essential guide to finding them.