Nombre en español: Halcón-montés Ojiblanco
Nombre en inglés: Lined Forest-Falcon
Nombre científico: Micrastur gilvicollis
El halcón montés cabecigrís (Micrastur gilvicollis) es una especie de ave accipitriforme de la familia Falconidae que vive en Sudamérica.
Es un halcón pequeño que mide entre 33 y 38 cm de longitud. Las partes superiores de su cuerpo son de color gris mientras que las inferiores son blancas con finas franjas horizontales negras. El halcón montés cabecigrís junto al halcón montés críptico y halcón montés plomizo forma un complejo críptico de especies. Los adultos de estas tres especies tienen el lorum pelado de color anaranjado al igual que su cera, lo que los diferencia del halcón montés agavilanado, pero solo el halcón montés cabecigrís tiene dos líneas blancas en la cola, además del borde blanco.
Distribución y hábitat
Se encuentra en las selvas húmedas del norte y el oeste de la cuenca del Amazonas. Está presente en Bolivia, Brasil, Colombia, Ecuador, Guayana francesa, Guyana, Perú, Surinam y Venezuela.
Lined forest falcon
The lined forest falcon (Micrastur gilvicollis) is a species of bird of prey in the family Falconidae. It is endemic to humid forest in the western and northern Amazon Basin. Populations found in the south-eastern Amazon Basin (south of the Amazon River and east of the Madeira River) were formerly included in this species, but were described as a new species, the cryptic forest falcon, in 2003. Together with the plumbeous forest falcon of the Chocó, they are an example of a cryptic species complex. While adults of all three species have the deep orange-red facial skin and cere that separates them from the sympatric barred forest falcon, only the lined forest falcon has two white bars in the tail (in addition to a narrow white tail-tip). The species is listed by the IUCN as a species of least concern, indicating that populations are not in decline.
Lined forest falcon (Micrastur gilvicollis) was not recognized as a distinct species until 1972, when Schwartz separated the special from Barred Forest-Falcon (M. ruficollis.)
The Lined Forest-Falcon is a small forest raptor of the Amazon basin and northern South America. It has gray upperparts, pale underparts with narrow dark barring, yellow fleshy facial skin, long legs, and a long, rounded tail. It is separated from the similar and sympatric Barred (M. ruficollis) and similar but allopatric Cryptic (M. mintoni) and Plumbeous (M. plumbeus) forest-falcons by its distinctive voice as well as the unique combination of white irides and two narrow white tail bands. The call is two-noted, both notes descending, the second slightly higher overall than the first. The Lined Forest-Falcon occurs in tall rainforest, where birds call at dawn and dusk from high in trees but generally hunt in lower forest strata. Its feeding behavior is poorly-documented, but it is known to prey on birds and snakes and occasionally follows army ant swarms. There is no verified nesting record or associated breeding information.
33–38 cm; 170–262 g (average 209 g); wingspan 51–60 cm. Back pale grey; white below, with barring very variable in extent, from heavy all over, to much lighter and restricted to breast; dark tail has white tip and 2 (occasionally 1) narrow white bars. typically reddish-orange, legs and feet yellow. Differs from M. ruficollis in colour of irides, number of tail bars (fewer), tail length (shorter), and wing length (longer), the latter resulting in very different wing/tail ratios for the two species. Differs from M. plumbeus in tail pattern. Immature slightly browner; irides brown to yellowish; cere, lores and orbital ring yellow.
Name pelzelni is a synonym of this taxon. A member of the M. ruficollis clade. Recently split as valid species from M. ruficollis. Often considered to include M. plumbeus as race. Monotypic.
E Colombia through S Venezuela to the Guianas, and S throughout Amazonia.
Prefers undisturbed primary tropical forests video in lowlands and foothills, although occurs in reduced densities in disturbed forest and forest edge in some areas. In Colombia and Ecuador favours humid terra firme forest. May range up to 1600 m in elevation.
Probably largely sedentary. Three radio-tagged birds followed from Mar–Jun in Brazil had home ranges of 20–67 ha in contiguous undisturbed forest.
Diet and Foraging
Not well documented. Lizards and large insects; some birds; in French Guiana, mostly snakes. Hunts primarily in forest understorey . Follows army ant swarms, although less frequently and for shorter periods than M. ruficollis. Takes some birds (causes considerable mortality amongst birds trapped in mist nets), but does not have foot structure of specialist on avian prey; passerines foraging near it, over army ant swarms, do not seem particularly afraid of it, in contrast to their behaviour when a small Accipiter approaches. One captured in mist net at 1570 m in Peru was carrying a short-tailed opossum (Monodelphis sp.).
Sounds and Vocal Behavior
Most common vocalization is a nasal «cow-káh», «cow káw-káw»audio or «cow káw-káw-káw»audio (first note lower and less emphasized than following notes) given over and over at intervals of 1·5–2·5 seconds, most typically before dawn and during wet weather. Tonal quality more nasal and lower pitched than that of M. ruficollis. Occasionally calls in longer series when excited.
Almost no information, despite the species being widespread and relatively abundant. Only reported nest was a stick nest, but this would be uncharacteristic of Micrastur and probably was a misidentification, given that all verified nests for the genus have been in tree cavities (although the possibility of the species using a stick nest built by another species cannot be ruled out (3) ). Tail of a female trapped near Manaus, NC Brazil, was dirty, bent and broken off (all feathers roughly same length), as would be expected if the bird had been incubating in a small tree cavity. Breeding biology probably similar to closely related M. ruficollis.
Not globally threatened (Least Concern). CITES II. Probably the most abundant diurnal raptor over much of lowland forest of Amazonia, where it attains very high densities; territories in central Amazon are c. 100 ha, with fairly even distribution throughout the forest. Average estimated density of at least c. 70 individuals/10,000 ha of forest in French Guiana in early 1980s, where the only raptor species apparently more abundant was Ibycter americanus. No estimate of global population size or population trends, but 8000–24,000 breeding pairs estimated to occur in French Guiana on the basis of surveyed densities of 2–6 pairs/20 km2 from 1981–2003.