Chestnut-crested Antbird Rhegmatorhina cristata Scientific name definitions

This, the northwestern representative of the ‘professional’ antbird genus Rhegmatorhina occurs in southeast Colombia through adjacent northwest Brazil entirely west of the Rio Negro. The species appears to prefer tropical evergreen forest on nutrient-poor, sandy soils, and it is perhaps entirely confined to such areas. Its range is not easy to penetrate and comparatively few natural history observations had been published for this species until recently. The Chestnut-crested Antbird feeds on arthropods, which are usually flushed by the army ant swarms that the birds follow for the majority of each day. It joins other obligate ant-following birds, including White-chinned Woodcreepers (Dendrocincla merula) at these swarms, the different individuals constantly attempting to displace each other and all the while uttering harsh, churring calls, but this species is apparently always subordinate to Reddish-winged Bare-eyes (Phlegopsis erythroptera) when the latter is present. Nothing is known concerning this antbird’s breeding ecology. Like its congeners, the Chestnut-crested Antbird is a striking-looking bird, the largely rufous and brown plumage made replete by the black face and throat, and bluish-gray periorbital skin.

14–15 cm. Large periorbital patch pale bluish-white; short crest. Male has crest and nuchal collar rufous-chestnut; upperparts, wings and tail dark olive-brown, wings edged rufous; forehead, lores, side of head and throat black, underparts rufous-chestnut, becoming dark olive-brown posteriorly. Female is similar to male, but with short black bars on back and lesser wing-coverts.

SE Colombia (Vaupés, E Caquetá, N Amazonas) and adjacent W Brazil (E along R Uaupés and S, W of R Negro, to Jaú and lower R Japurá).

Undergrowth of humid lowland evergreen forest , generally, perhaps always, on sandy soils; to 350 m.

Presumed resident.

Feeds on variety of arthropods, virtually all obtained when flushed by army-ant swarms. Recorded prey include crickets (Gryllidae), cockroaches (Blattidae), grasshoppers (Acrididae), ant larvae (Formicidae), spiders. Forages mostly below 1 m; multiple pairs or family groups may concentrate at some ant swarms; does not associate with mixed-species flocks, but often forages in presence of other species at swarms. Considered an obligate follower of army ants, faithfully following swarms primarily of Eciton burchelli. Early in morning, cruises through the forest individually, in pairs or in family groups, moving 1–2 m above ground in search of ants, frequently first checking raiding paths and bivouac sites from previous day; if not successful, wanders more widely, immediately investigating vocalizations of conspecifics and of other obligate followers; once located, swarms are generally followed for most of day. Progresses mostly by short, fluttery flights; tail regularly lowered to as much as 80 degrees below body level, then rapidly flicked up to as much as 30 degrees above plane of body; crest frequently erected and lowered. Perches generally 0·1–0·5 m above ground, often clinging laterally (upper leg flexed, lower one extended) to thin vertical stems, pitching yawing and pivoting with great agility; also uses horizontal perches on fallen branches, root buttresses, and stilts of stilt-rooted trees. Makes rapid, darting sallies and pounces to the ground to seize fleeing arthropods, before quickly hopping or flying to another perch before ants can counter-attack; less often makes short aerial sallies or sallies to foliage, vines, branches and trunks; occasionally tosses dead leaves from litter with flicking motions of the bill to uncover prey taking refuge from ants. Most prey are between one-third and 1·5 times the length of bird’s bill; larger items often removed to a perch away from swarm centre and dissected or dismembered, normally by using the bill to hold a leg of the prey and then shaking it until the leg comes off; does not hold prey in feet, nor bash them against substrate. Often wipes the bill vigorously against branches after dealing with large prey. Frequently noisy and combative at ant swarms, where conspecifics supplant one another and other species from perches above most productive parts of swarm. Dominant over Gymnopithys leucaspis, Pithys albifrons and Willisornis poecilinotus, and recorded as supplanting White-chinned Woodcreeper (Dendrocincla merula), but is subordinate to and readily displaced by Phlegopsis erythroptera.

Loudsong a series of whistles, length variable (e.g. 7–9 notes, 3·5–4 seconds), first note long and flat, second higher-pitched and down­slurred, following notes gradually become more downslurred and lower in pitch. Calls include harsh, vibrant “chirr”, diminishing slightly in pitch and intensity, and abrupt “chip”.

Almost nothing known. Male in breeding condition on 16th May in Colombia (Mitú); family groups with independent juveniles in mid-Aug in Brazil (São Gabriel da Cachoeira).

Not globally threatened. Restricted-range species: present in Orinoco-Negro White-sand Forests EBA. Uncommon to locally fairly common. Has small range, but this currently under relatively little development pressure. The known range of this poorly known thamnophilid in Brazil has been greatly extended since 1995, when it was first found at São Gabriel da Cachoeira, while recent discovery of the species within the huge Jaú National Park (2,272,000 ha) should ensure an adequate protected area. More surveys are needed in order more accurately to assess its distributional limits and densities, both within and outside Jaú. Considered highly sensitive to human disturbance.