Cryptic Forest-Falcon Micrastur mintoni Scientific name definitions

During the dawn chorus in lowland terra firme forest at Caxiuanã, Pará, Brazil one morning in 1997, Andrew Whittaker recorded the vocalizations of a forest-falcon that he could not immediately place into any known species. After playback of the recording, he coaxed a small forest-falcon into the open. It looked almost exactly like the common Lined Forest-Falcon (Micrastur gilvicollis), yet in addition to its distinctive vocalizations, there were also subtle plumage differences. After examining museum specimens and an exhaustive analysis of forest-falcon recordings, Whittaker described this distinctive form as a new species, the Cryptic Forest-Falcon. It is a testament to how poorly known forest-falcons are that such a large bird that is widespread in southeastern Amazonia - ranging south of the Amazon, east of the Rio Madeira and west and south to the southern edge of humid lowland forest - could have remained unrecognized for so long.

30–35 cm; male 171–238 g (n = 8), female 170–264 g (n = 11) (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 ). Plumage is slaty grey above, often darker on top of head, and with upperwing and rump more blackish; tail slightly darker than remiges, broad white central band (55 mm from tail tip, 62 mm from base), can have a second white band nearer base (hidden under uppertail-coverts), all rectrices with pale greyish tips; white chin and central throat surrounded by grey, white on rest of underparts, the breast with fine blackish-grey bars (barring becoming gradually stronger towards lower throat/upper breast), entirely or mostly unbarred flanks and lower belly often with irregular dark staining (mostly towards centre of lower belly), thighs with well-spaced fine dark bars; axillaries and underwing-coverts white, undertail blackish-grey with white central bar; iris white, often with slight greyish cast; bill black, base orange-yellow; cere and bare areas on face (lores, nostrils and circumorbital area, including eyebrow) bright orange ; legs and toes orange-yellow, claws mostly blackish with paler bases. Differs from other forest-falcons in having short tail (wing:tail ratio 1·36, compared with 1·29 for M. gilvicollis), single broad white central tailband (sometimes a weak additional band concealed by uppertail-coverts) (2 Whittaker, A. (2013). Unravelling the forest falcons to expose a hidden species: Cryptic Forest Falcon. Neotropical Birding. 12: 25-30. Close ), bare bright orange skin extending above whole eye (in <em>M. gilvicollis</em> only above anterior three-quarters of eye), dark barring below well defined only on breast and greatly reduced on belly, and no buff wash. Female is like male, but generally more boldly barred below. Immature has two distinctly narrower white bands across tail, and below has buff wash with barring much reduced; iris dark to greyish (white in subadult); some young have bold diagonal line across lower cheek.

A member of the M. ruficollis clade. For more than a century, specimens of present species were erroneously labelled as M. gilvicollis (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 , 2 Whittaker, A. (2013). Unravelling the forest falcons to expose a hidden species: Cryptic Forest Falcon. Neotropical Birding. 12: 25-30. Close ). First detected as a separate species when its distinctive voice was noted in the field as clearly different from that of all its congeners; museum specimens confirmed that it differs also, albeit somewhat subtly, in several morphological features. Isolated population in Atlantic Forest of E Brazil shows subtle plumage variations and may represent distinct race, but more data required. Monotypic.

Locally in E & S Amazonian Brazil (Pará and W Maranhão S to Rondônia) and NE Bolivia (N Santa Cruz); also E Brazil, with recent sightings in Espírito Santo, and historical specimens from both this state and S Bahia.

Lowland terra firme forest with tall trees and a dense understorey with many palms, vines and epiphytes; also frequents seasonally flooded várzea forest with bamboo in understorey (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 ). Atlantic Forest in E Brazil. Like other members of genus, it is an inconspicuous and elusive raptor of forest interior, far more frequently heard than seen. Replaces M. gilvicollis S of R Amazon and E of R Madeira.

Little information. Diet known to include reptiles and invertebrates (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 ); some small birds also likely prey, and one bird showed signs of trying to capture Rufous-necked Puffbird (Malacoptila rufa) as its loudsong was played from tape recorder within thick, dense forest undergrowth (3 Whittaker, A. (2009). Pousada Rio Roosevelt: a provisional avifaunal inventory in south-western Amazonian Brazil, with information on life history, new distributional data and comments on taxonomy. Cotinga 31:23–46. Close ). Believed to be a generalist; typically watches from low, concealed perch in understorey, dashing out to seize prey. Sometimes attends army-ant (Formicidae: Cheliomyrmecini and Ecitonini) swarms to take advantage of small fleeing animals (3 Whittaker, A. (2009). Pousada Rio Roosevelt: a provisional avifaunal inventory in south-western Amazonian Brazil, with information on life history, new distributional data and comments on taxonomy. Cotinga 31:23–46. Close ).

Three distinct vocalizations known (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 ): commonest is territorial advertising song, which consists of repetition of single low-pitched notes at 1 note per second, “uk uk uk uk...”, typically lasting for 1–1·5 minutes; excited cackling call is a series of short, fast, cackled “ca ca ca-ca-ca” notes, speeding up and sounding like a bouncing object going downscale, repeated every 1–2 seconds; third, and least frequently heard, vocalization is quacking song , consisting of three loud, lamenting notes, “uuk, qui, qua-qua” (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 ). Frequently vocalizes at dawn, and occasionally, during dry season, later in morning; less often heard just before dusk.

Very little information. Suspected to nest in wet season (Dec–May) on the basis of birds molting remiges from Apr–Aug and an adult female collected in early Jun having heavily abraded rectrices, possibly indicating damage from nesting cavity (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 ). Food-begging recorded in Sept, during dry season, in Mato Grosso (SC Brazil). Presumed to breed in cavities, as do congeners.

Not globally threatened (Least Concern). Little information; probably fairly common, although easily overlooked. Transect of virgin forest in Santa Cruz, Bolivia, yielded densities as high as 3–4 pairs/km at dawn during dry season (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 ); territorial density predicted to be similar to that of M. gilvicollis, as high as 1 pair/20–67 ha. Status of population in E Brazil appears to be critical; last documented record from this region was, until very recently, a specimen collected in 1933, since when extensive destruction of lowland Atlantic rainforest has taken place; sight records in 1990s and possible tape recordings in 2011, suggested this population still exists, and were confirmed in Jul–Aug 2012, when species was photographed  several times in privately owned reserve of Linhares, Espírito Santo (4 Simon, J.E. and Magnago, G.R. (2013). Rediscovery of the Cryptic Forest-Falcon Micrastur mintoni Whittaker, 21431432 (Falconidae) in the Atlantic forest of southeastern Brazil. Revista Brasileira de Ornitologia. 21(4): 257–262. Close ), and subsequently, in Jun 2014, photographic documentation  was also obtained from EC Bahia; urgent research required to establish survival and remaining range of this isolated population; it may represent a separate taxon, and, if it survives, is almost certainly critically endangered. Populations in Amazonia probably not at any immediate risk. However, based on a model of future deforestation in the Amazon basin (5 Soares-Filho, B. S., D. C. Nepstad, L. M. Curran, G. C. Cerqueira, R. A. Garcia, C. A. Ramos, E. Voll, A. McDonald, P. Lefebvre, and P. Schlesinger (2006). Modelling conservation in the Amazon Basin. Nature 440:520–523. Close ), this species is expected to lose 34–51% of habitat within its distribution over three generations (25·8 years) (6 Bird, J. P., J. M. Buchanan, A. C. Lees, R. P. Clay, P. F. Develey, I. Yépez, and S. H. M. Butchart (2011). Integrating spatially explicit habitat projections into extinction risk assessments: a reassessment of Amazonian avifauna incorporating projected deforestation. Diversity and Distributions 18(3):432–439. Close ). Furthermore, an analysis of global forest cover change from 2000 to 2012 (7 Hansen, M. C., P. V. Potapov, R. Moore, M. Hancher, S. A. Turubanova, A. Tyukavina, D. Thau, S. V. Stehman, S. J. Goetz, T. R. Loveland, A. Kommareddy, A. Egorov, L. P. Chini, C. O. Justice, and J. R. G. Townshend (2013). High-resolution global maps of 21st-century forest cover change. Science 342(6160):850–853. Close ) reveals that this species has lost 22% of its habitat within its entire distribution over three generations (8 Tracewski, L., S. H. M. Butchart, M. Di Marco, G. F. Ficetola, C. Rondinini, A. Symes, H. Wheatley, A. E. Beresford, and G. M. Buchanan (2016). Toward quantification of the impact of 21st-century deforestation on the extinction risk of terrestrial vertebrates. Conservation Biology 30(5):1070–1079. Close ), suggesting that it should be considered globally Near Threatened. It is not considered of conservation concern in Brazil (9 MMA (2014). Lista Nacional Oficial de Espécies da Fauna Ameaçadas de Extinção. Portaria No 444, de 17 de dezembro de 2014. Diário Oficial da União - Seção 1. Nº 245, quinta-feira, 18 de dezembro de 2014. Close ).