Mauritius black bulbul  (Hypsipetes olivaceus)

Classified as Vulnerable (VU) on the IUCN Red List (1).

The Mauritius black bulbul is a rare passerine with a dull plumage comprising various shades of olive-green and grey (2). The head is mostly olive-grey, with dark, almost blackish, pointed crown feathers, and the upperparts are a dark greenish-olive (2) (3) (4). Underneath, the throat, breast and flanks are more of a greenish grey, while the belly has a tinge of yellow (2). The pinkish-yellow, or orange, of the bill and legs stands out conspicuously against the dull plumage. The sexes are similar in appearance, but the male is on average slightly larger. Several different nasal and wheezy calls are recognised, including a ‘chuckle’ used in various different contexts (2) (3) (4). In the past, the Mauritius black bulbul was considered conspecific with the Reunion bulbul (Hypsipetes borbonicus), but genetic studies have now shown them to be separate species (2) (3).

The Mauritius black bulbul is endemic to the Indian Ocean island of Mauritius, where it occurs at low densities over southern and central parts of the plateau (2) (5).

Although the Mauritius black bulbul favours native evergreen broadleaved forest on steep slopes and in gullies, it also forages in forest margins, degraded forest and exotic plantations (3) (4).

Like many bulbuls, the Mauritius black bulbul mainly feeds on a diverse range of fruit, but will also take arboreal insects such as bush crickets, butterflies, caterpillars and stick-insects, and will sometimes take small vertebrates such as native geckos (Phelsuma sp.) (2) (3). The foraging habit of this species is strictly arboreal, with food items seldom collected from the ground (2).

The Mauritius black bulbul is usually found in pairs or small groups of up to eight individuals (2) (3). Nesting has been observed between November and February, with breeding pairs defending a small territory, within which the female builds a coarse nest around two to nine metres off the ground in a low bush or tree. Usually around three eggs are laid, which are incubated for 15 to 16 days before hatching. The young are fed by both parent birds and may remain in the same territory for some time (2).

Since humans colonised Mauritius in the 17th century, the combination of hunting, introduction of alien plants and animals, deforestation, and farming has dramatically altered the island’s biodiversity (6) (7). The spread of non-native plants that are poor in food has been particularly detrimental to the Mauritius black bulbul, which has maintained a steady but extremely small population of just 280 pairs for the last three to four decades (2) (3) (5). Additional threats to this species include predation by introduced rats and the crab-eating macaque (Macaca fascicularis), and competition with the introduced red-whiskered bulbul (Pycnonotus jocosus) and common mynah (Acridotheres tristis) (2) (3).

Partial protection within the Black River National Park, and the exclusion and eradication of invasive plants and animals in Conservation Management Areas, has been crucial to the survival of the Mauritius black bulbul. The long-term aim for the conservation of this species is to continue the rehabilitation of native vegetation and to potentially translocate some Mauritius black bulbul populations to nearby islets free from predators (3).

View information on this species at the UNEP World Conservation Monitoring Centre.

To find out more about the conservation of the native birds of Mauritius, see:

• Mauritian Wildlife Foundation:
  www.mauritian-wildlife.org

For more information on this and other bird species please see:

• BirdLife International:
  http://www.birdlife.org