Most Strigidae species are monogamous with long term pair bonds. They usually breed once per season, due to the length of the breeding cycle and post-fledging care.
The breeding period is generally related to food availability.
Information about the courtship displays is needed for this species, but more generally, the displays of the Strigidae are thus described:
During the breeding season, the male utters vocalisations during one month before the nesting period, in order to attract a female or to renew the pair-bond with its mate. Displays include wing-clapping by slapping the wings beneath the body during the flight. Pairs fly and circle together over the territory, and the males perform courtship displays high in the sky. Courtship feeding is often observed, with female begging food as a young bird, and male performing wings and body displays before copulation. (See Page Order Strigiformes)
The Usambara Eagle-Owl is probably resident within its restricted-range. Some altitudinal movements probably occur depending on weather conditions. But more studies are required.
The flight is silent, thanks to the soft flight-feathers.
REPRODUCTION OF THIS SPECIES:
The breeding season takes place from October to February.
The Usambara Eagle-Owl probably nests in tree holes and other natural (or not) cavities.
The female usually lays two white eggs, rarely three or four. She incubates alone and broods the chicks, while the male provides the food.
From some observations, a downy chick was seen in November, and a fledgling (not able to fly) in April.
The juveniles depend on adults for a long period, and this species produces a single brood per season. No more information.
PROTECTION / THREATS / STATUS:
The Usambara Eagle-Owl is threatened by habitat loss caused by forest clearance and fragmentation. However, the species is present in several protected areas throughout the range.
The population is roughly estimated to number 200/1000 individuals. But recent discovery of populations at other locations (Uluguru and Udzungwa Mts) indicates that the numbers maybe greater.
This population is suspected to be declining.
The Usambara Eagle-Owl is currently listed as Vulnerable.
Fr: Grand-duc des Usambara
Ang: Usambara Eagle-Owl
All: Usambarauhu
Esp: Búho de Usambara
Ita: Gufo reale degli Usambara
Nd: Usambaraoehoe
Sd: usambarauv
Photographer:
Dubi Shapiro
Dubi Shapiro Photo Galleries
Text by Nicole Bouglouan
Sources:
HANDBOOK OF THE BIRDS OF THE WORLD Vol 5 by Josep del Hoyo-Andrew Elliott-Jordi Sargatal - Lynx Edicions - ISBN: 8487334253
OWLS OF THE WORLD – By Claus König, Friedhelm Weick and Jan-Hendrik Becking - IBSN 978-0-7136-6548-2
BIRDS OF PREY OF AFRICA AND ITS ISLANDS by Alan and Meg Kemp - Struik Publishers - ISBN: 1770073698
Wikipedia, the free encyclopaedia
Usambara Eagle-Owl
Bubo vosseleri
Strigiformes Order – Strigidae Family
INTRODUCTION:
The Usambara Eagle-Owl is today a full species, but formerly, it was considered a subspecies of the Fraser’s Eagle-Owl (Bubo poensis) which is paler and smaller.
The Usambara Eagle-Owl is endemic to the Usambara Mountains in NE Tanzania. These mountains are fairly unusual in E Africa, as they are covered in tropical forests, a type of habitat mostly found in W Africa. This area has gone through a long term and unique evolution, due to the lack of glaciations and a consistent climate, with the result of numerous endemic plant and animal species, and old-growth cloud rainforest.
The Usambara Eagle-Owl also frequents the forested edges of tea plantations in lowlands, but it is more frequently observed between 900 and 1,500 metres of elevation. It typically feeds on small mammals and birds, reptiles and large arthropods. It nests in tree holes and the juveniles probably depend on adults for a long period.
The Usambara Eagle-Owl is a restricted-range species threatened by forest clearance. It is currently listed as Vulnerable.
DESCRIPTION OF THE BIRD:
Biometrics:
Length: 45-48 cm
Weight: 770-875 g
The Usambara Eagle-Owl is very similar to Bubo poensis, but it is larger and darker.
The upperparts are reddish-brown with darker brown barring on crown, mantle and back. The paler edges of the scapulars form an indistinct pale row on the shoulder. Wings and tail show regular reddish-brown and dark brown barring.
On the underparts, the pale, tawny-ochre breast is densely spotted dark brown. Over much of the rest of the underparts, this pattern becomes paler, with whitish-buff mottling and irregular darker barring. Belly and flanks are whitish-buff with fine darker bars. On the underwing, the coverts are orange-brown and the whitish flight-feathers are broadly barred black. The undertail is whitish with regular, narrow dark bars.
On the head, the ear-tufts are brown. The facial disk is pale orange-rufous with conspicuous dark rim, becoming broader when joining the neck. Eyebrows are absent.
The bill is yellowish to greyish-horn. We can see long, dark rictal bristles. The eyes are orange-brown. Legs and feet are dull yellowish with dark claws.
Male and female are similar.
The juvenile is dull yellow with fine brown barring on back and underparts. Flight-feathers and rectrices are pale orange-brown with dark barring.
On the head, the blackish-brown ruff and the blackish bristles contrast with the pale face. The ear-tufts are spotted brownish. Bill and legs are pale bluish.
RANGE:
The Usambara Eagle-Owl is endemic to Tanzania. It is mainly found in the Usambara Mountains on the NE, but the species has been recently discovered in the Uluguru Mountains in E Tanzania, and Udzungwa Mountains in SC Tanzania.
There is also a possible sighting in the Nguru Mountains, a part of Eastern Arc Mountains.
HABITAT:
The Usambara Eagle-Owl is primarily found in subtropical or tropical moist forest, usually between 900 and 1,500 metres of elevation. It also frequents the forested borders of tea plantations, down to 200 metres, where it is frequently observed.
However, regional variations are reported depending on the range but mainly in the Usambaras, whereas in the other parts of the distribution, it is only known at 1,550 metres in the Ulugurus, and between 1,200 and 1,700 metres in the Udzungwas.
CALLS AND SONGS: SOUNDS BY XENO-CANTO
The Usambara Eagle-Owl gives a low-pitched “po-a-po-a-po-a-po” lasting about 5-7 seconds and repeated after 30-60 seconds, up to four times. This song is only given at night.
BEHAVIOUR IN THE WILD:
The Usambara Eagle-Owl typically feeds on small mammals and birds, but also frogs, reptiles and large arthropods.
As the Fraser’s Eagle-Owl is known for feeding almost entirely on insects, we can suggest that the diet of the Usambara Eagle-Owl includes numerous insect species too.
The main hunting style of this species and more generally of Bubo’s species is “sit-and-wait”, dropping or gliding from high perch to attack a prey on the ground.
