African Grass-Owl

识别特征

The African grass owl resembles the barn owl and has a heart shaped whitish-cream facial disc, with a narrow yellowish-buff rim which is densely spotted dark. The eyes are brownish-black, and the bill is whitish to pale pink. The entire upperparts from the crown to the lower back and wing-coverts are a uniform sooty blackish-brown, with scattered small white spots and greyish flecks. The primary feathers and secondary feathers are pale brownish-grey with dark bars and yellow bases. The short tail has uniform brown central feathers fading to paler, almost white, outer feathers which show about four dark bars. The underparts vary in colour from whitish to buff marked with dark spots. The legs have whitish feathers which extend to the lower third of the tarsi. The lower leg and feet are slightly bristled and coloured pale yellowish-grey. The body length is 38–42 cm (15–17 in), the wing length 283–345 mm (11.1–13.6 in) and they weigh between 355 and 520 g (12.5 and 18.3 oz). A high degree of sexual dimorphism is present, whereby the body mass and length is significantly larger in females than in males. This is a consequence of observable differences in hunting techniques and efficiency of brooding.<p>They have a screeching call which is similar to that of the Barn Owl, but it is less strident. A high-pitched sibilant tremolo lasting one to two seconds is thought to be the song of the male.

分类信息

学名

Tyto capensis

命名信息

(Smith, A, 1834)

目

Strigiformes

科

Tytonidae

属

Tyto

分布与栖息地

It is distributed in sub-Saharan Africa where there are two blocks of its main range, one in central southern Africa across southern Congo and northern Angola to the central coast of Mozambique and the other centred on South Africa from the Western Cape north to the southern extremities of Zimbabwe, Botswana and Mozambique. There are isolated populations in the Ethiopian Highlands, Kenya and Uganda and Cameroon. The African grass owl is found in moist grassland and open savanna up to an elevation of 3,200 m (10,500 ft). In east Africa it may also be found in dry grassland and at higher altitudes in Aberdares and on Mount Kenya. In southern Africa this species generally prefers marshes and vleis where there are patches of tall, rank grass and other vegetation but it may also be found in fynbos, renosterveld and acacia scrub close to water. The specific habitat requirements of the African grass owl characterize it as a habitat specialist.

迁徙

Resident species

保护状况

The African grass owl is evaluated as Least Concern. However, in South Africa the species is regarded as vulnerable because habitat degradation through ploughing, grazing, draining and burning; the population in the country is considered to be fewer than 5,000 individuals.<p>The habitats in which this species breeds and feeds are often alongside areas of human activity, such as industrial, agricultural or mining areas. This causes exposure to various environmental contaminants, for example, metals, which can subsequently be monitored using the birds' feathers. The African grass owl is a good bioindicator species.<p>To combat their state of vulnerability in South Africa, programmes of captive breeding and release for the African grass owl were tested and studies revealed that this may be a possible effective conservation strategy. However, reintroduction of the African grass owl is not a simple process because supplementary feeding is required and the habitat must be suitable and contain sufficient prey.

种群趋势

declining