Oma’o  (Myadestes obscurus)

Classified as Vulnerable (VU) on the IUCN Red List 2006 (1).

This small, drab thrush has a grey-brown head, olive-brown upperparts, and pale grey underparts. The bill and legs are blackish. Juveniles have dark brown upperparts, heavily spotted with a whitish-buff (2). Throughout the year, both males and females can be heard on their perches singing a pleasant, jerky melody, and males also perform a flight-song display known as “skylarking” (2) (3). Due to their dull, inconspicuous appearance, they are often detected firstly by their voice (4).

Endemic to Hawaii, in the Hawaiian Islands (2).

The oma’o inhabits mesic and wet native forests above 1,000 meters, which are characterized by a closed forest canopy, and an understorey composed of a variety of fruiting trees. It also occurs at lower densities in scrub and savannah, and one population is known to occur in treeless alpine scrub above 2,000 meters (2).

The oma’o is generally a solitary bird, but can be found in pairs throughout the year, with pair bonds lasting at least one breeding season (4). The breeding season lasts from January to the end of October (2), with females bearing the responsibility of constructing the nest, and incubating the one or two eggs that are laid (4). The nest is a loose, bulky cup of ferns, moss, leaves and small twigs, sometimes lined with grass, pine needles or flower parts (2). Incubation lasts for about 16 days, and the young remain in the nest for about 19 days before fledging. Both sexes feed the nestlings, and both adults provide parental care for five to six weeks after the young birds leave the nest (4), although they may remain in the natal territory for up to six months (2).

Oma'os are primarily frugivorous, feeding on a wide variety of fruits from understorey shrubs and trees, however it also forages in the forest canopy for invertebrates (2), including earthworms, snails, spiders and insects (3). The oma’o rarely forages on the ground, except for the alpine scrub population, where the diet consists of low-growing berries, and terrestrial invertebrates (2).

The oma’o occurs in just a few localities on one island, and thus is vulnerable to threats, despite healthy population numbers at present (5). In the past, habitat clearance for firewood, timber, agriculture and pasture has resulted in the species inhabiting only 25 to 30 percent of its former range (2). Its current distribution has also been heavily influenced by the presence of introduced mosquitoes, which spread avian malaria and avian pox (2) (5). However, there is evidence that oma’o have developed some resistance to the current strains of these diseases, as this species persists, whilst others have disappeared. Nevertheless, the oma’o still occurs at greater densities above 1,500 meters, where mosquitoes are less common (4). A potential future threat is the introduction of a cold-tolerant mosquito, along with new avian diseases (4). Further pressure on the oma’o comes from the spread of feral predatory mammals, such as rats and cats, into upland forests. In addition, the degradation of habitat caused by feral ungulates, particularly pigs, is likely to have caused the destruction of native plants important to the oma’o’s diet (2) (3).

The oma’o occurs in several well-managed protected areas, such as the Hawaii Volcanoes National Park (6), and the Hakalau Forest National Wildlife Refuge (7). This follows efforts during the 1980s and 1990s to purchase, protect and manage remaining areas of natural forest above 1,500 meters (2) (4). There have also been efforts to control and fence out feral pigs, goats, cattle and sheep, but there has not been any evidence yet that this has resulted in an increase in bird numbers (4). The presence of rats continues to be a significant problem to the oma’o and other native Hawaiian birds, and thus the implementation of a rat control program has been proposed (3) (5).

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

For further information on the oma’o see NatureServe:
http://www.natureserve.org/explorer/index.htm

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

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