Fraser's eagle-owl

Fraser's Eagle-Owl (Ketupa poensis)

Fraser's eagle-owl, scientifically known as Ketupa poensis, is a species of African owl belonging to the Strigidae family. It was formally described in 1854 by British zoologist Louis Fraser, who named it after the island of Bioko, then known as Fernando Po, where the initial specimen was collected. This relatively small eagle-owl is distinguished by its prominent, fluffy ear-tufts and a facial disc that features a noticeable dark rim.

Distribution and Habitat

This species is widely distributed across the African tropical rainforests and is also found on Bioko Island. Its primary habitats include dense forests, forest clearings, and areas with cardamom plantations. Fraser's eagle-owl can be found from sea-level up to elevations of approximately 1,600 meters (5,200 ft) in regions like Cameroon.

Physical Description

The upperparts of Fraser's eagle-owl are a rufous and buffy brown, marked with darker barring. The pale scapulars have outer webs edged in dark, creating a pattern of pale dots across the shoulder. Its flight and tail feathers exhibit narrow light and dark bars. The underparts are pale rufous, gradually becoming whitish on the belly and undertail coverts. Females of the species are larger than males.

Behaviour and Ecology

Fraser's eagle-owl is primarily a nocturnal bird, roosting during daylight hours hidden in foliage, typically around 40 meters (130 ft) above the ground. Its roosting sites are often revealed by small, diurnal birds that mob the owl. Activity begins at dusk, with singing most frequent in the early evening and just after sunset, as well as shortly before dawn. The diet is varied, consisting mainly of small mammals such as mice, squirrels, and galagos, but also includes birds, frogs, reptiles, insects, other arthropods, and occasionally fruit.

Vocalization

The territorial song of the male is a distinctive, rapid, stuttering, and long deep, guttural trill, which has been compared to the sound of an electricity generator. Additionally, both sexes can produce a two-syllable hoot, which is stereotypically owl-like, with the second syllable being higher pitched and more whistled. This double hoot is repeated at intervals of 3–4 seconds and is said to resemble the hoot of the European tawny owl. Another call, a single soft mewing 'wooh,' is also made by both sexes. Like many owls, they communicate by snapping their bills.

Taxonomy and Subspecies

Fraser's eagle-owl is now placed in the genus Ketupa, which was introduced in 1831. Two subspecies are recognized: K. p. poensis, found from Sierra Leone to Uganda, central Democratic Republic of Congo, and northern Angola, and K. p. vosseleri, inhabiting northeastern Tanzania. The subspecies K. p. vosseleri has, at times, been considered a separate species, the Usambara eagle-owl.

Breeding

The breeding biology of Fraser's eagle-owl is not extensively documented. While singing has been reported in Gabon between June and September, breeding appears to occur throughout the year, with egg-laying dates varying geographically. Nestlings have been found on the ground, leading to speculation that they may nest there, although at least one nestling was observed in a tree cavity. The eggs are white and unmarked. Juveniles are thought to remain dependent on adults for an extended period, retaining their juvenile plumage for about a year.