Asio stygius
One of the world’s least-documented owl species, the stygian owl has a dark plumage and is found in parts of Mexico, the Caribbean and Central and South America. Vagrant visitors have occasionally been recorded in Texas and Florida, but otherwise it is not usually spotted in much of North America.
Stygian Owl
Stygian owls are remarkable for their particularly dark plumage, with a small blackish facial disk bordered by pale feathers. Their prominent dark ear tufts are an identifying feature of this species. Their wings and back are dark with lighter buff streaking. The breast and belly are pale buff, densely marked with deep black-brown barring.
The eyes are a piercing yellow, the bill is blue-black, and the legs and feet are grayish-pink.
Sexes are similar, although females are slightly larger and heavier.
Juvenile stygian owls are initially downy in appearance, and have an overall lighter gray and paler brown appearance than the dark, dusky adults of the species. Their bodies are heavily marked with dark barring, and their facial disk is less defined than in adults. The eyes of juvenile stygian owls are brownish-yellow and gradually become a clearer bright yellow with age and maturity.
Stygian Owl perched in natural habitat
A moderately large member of the owl family, the stygian owl is similar in size to a barn owl and a long-eared owl. Females are larger and heavier than males and have slightly longer wings.
Male stygian owls can be heard making a repetitive deep "whoof" with short intervals between calls. Females use a shrill “miah” scream in "miah", in response to the male. A noisy "wak-wak-wak" signals excitement, and young owlets make a “cheet” cry when hungry.
Birds form the chief element of a stygian owl’s diet, including blue-black grassquit, eared doves, and lesser nothura. Bats are also important, and frogs and insects are also eaten.
Stygian owls hunt from perches, targeting birds roosting overnight or catching bats in flight. Compared to other owl species, stygian owls are notable as their diet is not focused primarily on rodents.
Adult stygian owls bring prey to the nest, including regurgitated grasshoppers, crickets, and small birds that are torn up and fed to their young.
Stygian owls are known primarily as forest-dwelling owls, found in mountainous regions at elevations between 700 m to 3000 m (2300 ft and 10,000ft) above sea level.
Present in both tropical rainforests and both humid and semi-arid forested landscapes, stygian owls are usually absent from low-lying regions, although, in parts of Brazil and Belize, they are observed to hunt in savannah environments.
Eastern and southern Mexico forms the northern limit of the stygian owl’s usual distribution range. Scattered populations occur throughout Central America to Nicaragua. Stygian owls also have a presence in the Caribbean islands of Cuba and Hispaniola.
In South America stygian owls are resident from the extreme northwest of Venezuela through eastern Colombia and central Ecuador. A small population is found in north-central Brazil, with a larger area spreading from eastern Bolivia south through eastern Paraguay, northeastern Argentina, and into southern Brazil.
Stygian owls have a discontinuous range, and have been recorded as a native species in Mexico, the South American countries of Colombia, Venezuela, Ecuador, Brazil, Bolivia, Peru, Paraguay, and Argentina, and in Belize, Guatemala, Honduras, and Nicaragua in Central America. Stygian owls are also native to the Caribbean islands of Cuba, the Dominican Republic, and Haiti.
Despite having an expansive geographical distribution area, little is known about the population size or prevalence of stygian owls.
Only a handful of records exist from Venezuela and Nicaragua, while in Brazil it is thought to be more widespread and numerous. The overall population is unknown, but a wide estimate of 50,000 to 499,999 is suggested by Bird Life International.
Stygian owls are not normally resident in any part of the United States, with their northern range beginning from the state of Durango in western Mexico. However, occasional reports of vagrant individuals have been recorded in the southern US, including the first recorded sighting in Texas in 1996 at Bentsen-Rio Grande Valley State Park.
Due to an absence of in-depth research on the behavior and ecology of stygian owls, information about their lifespan and first breeding age is unknown.
Unusually for an owl species, stygian owls are known to prey on their own species, an adaptation known as intraguild predation, which is thought to occur to eliminate competition for food resources.
Across their range, stygian owls are protected under various local conservation acts. In Mexico, they are protected under the Endangered Species Act, while in Brazil, the Brazilian Wildlife Protection Act prohibits them from being killed, captured, traded, or injured.
Little is known about the threats and impacts of habitat change on the population numbers or future survival patterns of stygian owls, other than the global population is believed to be in decline. Worldwide, they are ranked as a species of least concern.
Stygian owls do not build their own nests, instead repurposing an abandoned tree nest of another bird. Ground-level nests are occasionally used.
Stygian owls’ breeding is timed to coincide with the rainy season, and timings differ from location to location. Nests are variously reported in March in central Brazil, in July in Belize, in September in southern Brazil, and in December in Cuba.
Incubation, by the female alone, lasts for around 30 days.
Eggs laid by stygian owls are plain white and rounded in shape, similar in size to table tennis balls. A typical clutch contains between 1 and three eggs.
From what little we know about the breeding habits of stygian owls, it appears that they are monogamous and will usually reunite to breed each year. Bonds are strengthened during courtship with males performing a wing-clapping display flight and females presenting males with food offerings.
Stygian owl perched high up in the forest trees
Aggressive hunting behavior is characteristic of stygian owls, who are observed to fearlessly attack prey that is much larger than themselves. Hissing and bill-snapping may be used when they feel their nest site is at risk.
Stygian owls are nocturnal, hunting during hours of darkness and roosting in dense vegetation during daylight hours. Empty cavities abandoned by other species may be used for roosting.
From all information available about the species’ habits and behavior, it appears that across their range, stygian owls are permanent residents and no migration occurs.
Stygian owls are not native to the US and the only records of the species in the country are as scarce vagrant individuals, limited to Florida and Texas. Sightings are not regular and no breeding has ever taken place in the United States.
Stygian owls have piercing golden-yellow eyes. Their eyes can appear to glow a fiery red when illuminated by artificial light.
Stygian refers to the Styx, the river of the Underworld in Greek mythology. The Styx was the river crossed by souls to reach the Underworld and formed the boundary of Hades. Today it has a wider meaning relating to being dark and gloomy, which reflects their dusky plumage.
Length:
38cm to 46cm
Wingspan:
96cm to 110cm
Weight:
500g to 700g
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