Nombre en español: Hormiguero del Yapacana

Nombre en inglés: Yapacana Antbird

Nombre científico: Aprositornis disjuncta

Familia: Thamnophilidae

El hormiguero del Yapacana​ (Aprositornis disjuncta), es una especie de ave paseriforme de la familia Thamnophilidae, la única perteneciente al género monotípico Aprositornis.​ Anteriormente formaba parte del amplio género Myrmeciza, de donde fue separada recientemente, en 2013.​ Es nativo del norte de la cuenca amazónica en Sudamérica.

Distribución y hábitat

Se distribuye de forma disjunta en el este de Colombia (Puerto Inírida y Caño Ima, Guainía), suroeste de Venezuela (oeste de Amazonas en las vecindades del Cerro Yapacana, poblado de Picua y margen izquierda del río Baría) y en el noroeste de Brasil (parque nacional Jaú, Amazonas y medio río Branco, Roraima).​

Esta especie es muy local, donde puede ser muy común, en su hábitat natural, el suelo o cerca, de bosque densos de sabana estacionalmente inundables y campinas arbustivas, por debajo de los 150 m de altitud.​

Sistemática

Descripción original

La especie A. disjuncta fue descrita por primera vez por el ornitólogo estadounidense Herbert Friedmann en 1945 bajo el nombre científico Myrmeciza disjuncta; localidad tipo «Cerro Yapacana, Amazonas, Venezuela.»​

El género Aprositornis fue descrito por los ornitólogos Morton L. Isler, Gustavo A. Bravo y Robb T. Brumfield en 2013.​

Etimología

El nombre genérico femenino «Aprositornis» deriva del griego «aprositos»: inalcanzable, difícil de aproximarse, y «ornis, ornithos»: ave; significando «ave difícil de aproximarse»;​ y el nombre de la especie «disjuncta», deriva del latín «disiunctus»: separado.​

Taxonomía

Hasta recientemente (2013), la presente especie estaba incluida en el amplio género Myrmeciza. La historia de este género se caracteriza por décadas de controversias e incertezas. Autores más recientes expresaron dudas consistentes en relación a la monofilia del grupo, pero no había ninguna revisión disponible que realmente probase la monofilia del grupo.​

El estudio de Isler et al. 2013 presentó resultados de filogenia molecular de un denso conjunto de taxones de la familia Thamnophilidae (218 de 224 especies). Estos datos suministraron un fuerte soporte a la tesis de que Myrmeciza no era monofilético y que sus miembros están distribuidos en tres de las cinco tribus de la subfamilia Thamnophilinae propuestas por Moyle et al. 2009. También se compararon las características morfológicas, comportamentales y ecológicas de las especies de Myrmeciza con sus parientes próximos dentro de cada tribu, con el objetivo de determinar los límites genéricos.​

Como resultado de estos análisis, los autores propusieron que las especies entonces situadas en Myrmeciza fueran reasignadas al propio género y a otros once, cinco de los cuales fueron resucitados: Akletos, Myrmelastes, Myrmoderus, Myrmophylax y Sipia, y seis de los cuales fueron descritos por primera vez: Ammonastes, Ampelornis, Aprositornis, Hafferia, Poliocrania, y Sciaphylax.​

En relación a la entonces Myrmeciza disjuncta, los datos suministraron un fuerte soporte a la existencia de un clado, que denominaron «clado Myrmorchilus», dentro de una tribu Microrhopiini (una de las cinco tribus de la subfamilia Thamnophilinae propuestas por Moyle et al 2009),​ integrado por Myrmorchilus y tres especies separadas del amplio Myrmeciza: M. atrothorax, M. pelzelni y la presente. Por sus características exclusivas, los autores sugirieron un género propio para cada una de las tres especies. Como no había un nombre disponible, para la presente especie fue descrito el género Aprositornis.​ En la Propuesta N° 628 al Comité de Clasificación de Sudamérica (SACC), se aprobó este cambio, junto a todos los otros envolviendo el género Myrmeciza.​

Los cambios fueron adoptados por la clasificación Clements checklist v.2017,​ y por el Congreso Ornitológico Internacional (IOC 2018, versión 8.1).​

La especie es monotípica.

​Yapacana antbird

The Yapacana antbird (Aprositornis disjuncta) is a species of passerine bird in the family Thamnophilidae. It is found in far eastern Colombia, southern Venezuela and northern Brazil. Its natural habitat is subtropical or tropical moist lowland forests.

The Yapacana antbird was originally described by the American ornithologist Herbert Friedmann in 1945 and given the binomial name Myrmeciza disjuncta. A molecular phylogenetic study published in 2013 found that the genus Myrmeciza, as then defined, was polyphyletic. In the resulting rearrangement to create monophyletic genera the Yapacana antbird was moved to its own genus Aprositornis. The name of the genus combines the Ancient Greek words aprositos «unapproachable» or «hard to get at» and ornis «bird».

Rather like the Gray-bellied Antbird (Myrmeciza pelzelni), which also occupies a similar, highly isolated, range at the border of three countries in the Negro–Orinoco drainage, much of our basic knowledge concerning the generally uncommon Yapacana Antbird has only been garnered very recently. This antbird, which is largely gray and whitish, with neat white wing-spots, in males, and gray and reddish brown in females, is seemingly restricted to stunted forest growing on white-sand soils, with abundant bamboo and sawgrass in the understory. The species occurs from eastern Colombia and southwest Venezuela south to far northwest Brazil, and has never been found above 150 m elevation. The Yapacana Antbird feeds on insects and spiders, which are sought either close to, or on, the ground, and does not join mixed-species flocks. Although its general behavior has now been reasonably well described, we still know virtually nothing concerning its breeding biology.

Distribution

Locally in E Colombia (Puerto Inírida and Caño Ima, Guainía), SW Venezuela (W Amazonas in vicinity of Cerro Yapacana, village of Picua and left bank of R Baría) and NW Brazil (Jaú National Park, Amazonas (and middle R Branco, Roraima).

Habitat

Seemingly restricted to understorey and floor of stunted, virtually impenetrable woodland growing on fine, compacted white-sand soils that are seasonally saturated; to 150 m. At Picua (Venezuela) this habitat referred to by local people as “monte cerrado”, having rather uniform canopy of 6–10 m with only scattered emergents, few trees thicker than 10 cm at breast height, and abundant bamboo and sawgrass in understorey.

Movement

Presumed resident.

Diet and Foraging

Feeds on insects, including orthopterans (Tettigoniidae, Gryllidae), hemipterans, and lepidopteran larvae (particularly of geometrid moths); also on spiders. Closely associated partners, individuals, or family groups forage to 1·5 m above ground, apart from mixed-species flocks; mostly on or near ground in dense vegetation. Active, restless forager, progressing by short hops, rarely pausing for more than 2 seconds to scan, usually taking erratic zigzagging path through understorey, with frequent abrupt changes of direction in both vertical and horizontal planes; agile and adept, clings laterally (with lower leg extended, upper one flexed) to slender vertical stems and vines; posture nearly horizontal, with head held higher than axis of body; regularly flicks the tail up and down in shallow 10-degree arc, also dips it slowly to 30 degrees below horizontal before rapidly flicking it back up, less frequently wags tail sideways in slow, somewhat jerky manner, similar to tail motions of Sclateria naevia; habitually flicks wings as it forages, flicks occurring both in and out of synchrony with tail movements. Moves on ground with a series of short hops with minimal pauses between movements, frequently hopping up to a low perch to scan before dropping back down; most frequent ground-foraging attack manoeuvres are gleans from surface of leaf litter or brief probes with the bill beneath the litter, followed by reaches up to glean from undersurfaces of overhanging green leaves and grass blades; commonly jump-gleans 6–15 cm upwards to underside of vegetation. When foraging above ground, perch-gleans most prey from stems, vines and upper and lower surfaces of live leaves, by reaching up, out or down on extended legs with neck craned; prey captured with quick stabs of the bill, and swallowed whole without handling; larger items bashed against perch repeatedly, and mandibulated one or more times before being consumed; typically, wipes bill on branch after swallowing prey. At least occasionally follows army ants in pursuit of flushed arthropods. A female at a swarm of Eciton ants was the only bird attending the swarm in over 20 minutes; part of the time she scanned the swarm from perches within 0·3 m of ground, dropped to the ground to seize fleeing arthropods, then returned to a low perch, but spent slightly more time in hopping between the columns of ants and tossing dead leaves from litter (with a quick flicking of the bill) to reveal prey hiding beneath.

Sounds and Vocal Behavior

Loudsong two prolonged (e.g. 0·8–1·5 seconds), harsh, frequency-modulated elements separated by short pause containing 1–2 abrupt “pip” notes, first harsh element longer and rises in pitch and intensity, second is more even; occasionally three harsh elements delivered. Calls include single long harsh note at higher pitch than notes of song, also abrupt “squip” which is sometimes repeated and extended into soft whistled notes, and soft rattle.

Breeding

Virtually nothing known. At Picua (Venezuela), birds were paired and territorial and responded strongly to tape playback in Jan and Feb, but seldom sang spontaneously (even at dawn), suggesting low levels of breeding during dry season; territories were tightly packed, estimated to be no more than 50–75 m in diameter.

Conservation Status

Conservation status on BirdlifeLC Least Concern Not globally threatened. Restricted-range species: present in Orinoco-Negro White-sand Forests EBA. Locally abundant. Habitat requirements appear to be highly specific. In Yapacana National Park, in Venezuela, 24 territories located along 1350 m of trail at Picua in 1998; elsewhere in the park, however, surveys of other scrubby woodland (not monte cerrado) on white-sand soils failed to reveal any additional territories, and the species has not been found in superficially similar savanna woodland in other parts of Amazonas state. Recent discovery of a population in the extensive (2,272,000 ha) Jaú National Park, in Brazil, extends the species’ known range some 500 km S. It occurs also in Pico da Neblina National Park, on Venezuela-Brazil border. Satellite imaging could help to determine the total amount of potential habitat within its known range; surveys needed in order to establish an approximate base population estimate. Continued protection of the national parks in which this thamnophilid is known to exist is critical, particularly with regard to exclusion of illegal gold-mining operations.

Fuentes: Wikipedia/eBird/xeno-canto/Birds of the world