Lined Forest-Falcon Micrastur gilvicollis Scientific name definitions

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) (1 Whittaker, A. (2002). A new species of forest-falcon (Falconidae: Micrastur) from southeastern Amazonia and the Atlantic rainforests of Brazil. Wilson Bulletin. 114(4): 421-445. Close ); wingspan 51–60 cm (2 Schulenberg, T. S., D. F. Stotz, D. F. Lane, J. P. O’Neill, and T. A. Parker (2007). Birds of Peru. Princeton University Press, Princeton, NJ, USA. Close ). 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. Irides white , facial skin 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 (3 Ferguson-Lees, J., and D. A. Christie (2001). Raptors of the World. Christopher Helm, London, UK. Close ).

Name pelzelni is a synonym of this taxon. A member of the M. ruficollis clade (4 Fuchs, J., Chen, S., Johnson, J.A. and Mindell, D.P. (2011). Pliocene diversification within the South American forest falcons (Falconidae: Micrastur). Molecular Phylogenetics and Evolution. 60(3): 398–407. Close ). 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 in lowlands and foothills (5 Ridgely, R. S., and P. J. Greenfield (2001). The Birds of Ecuador. Volumes 1–2. Comstock Publishing Associates, Ithaca, New York, USA. Close , 2 Schulenberg, T. S., D. F. Stotz, D. F. Lane, J. P. O’Neill, and T. A. Parker (2007). Birds of Peru. Princeton University Press, Princeton, NJ, USA. Close ), although occurs in reduced densities in disturbed forest and forest edge in some areas (6 Thiollay, J.-M. (2007). Raptor communities in French Guiana: distribution, habitat selection, and conservation. Journal of Raptor Research. 41(2): 90–105. Close ). 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 (7 Klein, B.C. and Bierregaard, R.O. (1988). Movement and calling behavior of the Lined Forest-falcon (Micrastur gilvicollis) in the Brazilian Amazon. Condor. 90(2): 497-499. Close ).

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.) (8 Socolar, S. J., O. González, and G. Forero-Medina (2013). Noteworthy bird records from the northern Cerros del Sira, Peru. Cotinga 35:26–38. Close ).

Most common vocalization is a nasal "cow-káh", "cow káw-káw" or "cow káw-káw-káw" (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 Ferguson-Lees, J., and D. A. Christie (2001). Raptors of the World. Christopher Helm, London, UK. Close ) ). 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 (9 Thiollay, J.-M. (1989). Area requirements for the conservation of rain forest raptors and game birds in French Guiana. Conservation Biology 3(2):128–137. Close ). 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 (6 Thiollay, J.-M. (2007). Raptor communities in French Guiana: distribution, habitat selection, and conservation. Journal of Raptor Research. 41(2): 90–105. Close ).