Large-billed blue-flycatcher  (Cyornis caerulatus)

The large-billed blue-flycatcher is classified as Vulnerable (VU) on the IUCN Red List (1).

This is a colourful flycatcher, named for its broad-based bill and habit of catching flying insects. Male and female large-billed blue-flycatchers differ significantly in appearance. Males have mostly dark blue plumage, with a rusty-orange breast and belly, fading to whitish on the underside of the base of the tail, while females have blue plumage on their rump and tail, elsewhere it is brown (2). Three subspecies of the large-billed blue-flycatcher are recognised; Cyornis caerulatus caerulatus is as described above, while males of C. c. rufifrons have deeper rusty-orange underparts, and C. c. albiventer is whiter on the lower belly (2).

The large-billed blue-flycatcher is endemic to Borneo and Sumatra. Subspecies C. c. albiventer inhabits Sumatra, C. c. rufifrons is found in west Borneo, while C. c. caerulatus occurs in northeast and south Borneo (2) (3).

The large-billed blue-flycatcher inhabits lowland primary forest, from sea-level up to around 500 metres (2) (3). It is found most often in the dense, tangled areas of the forest interior or at the edges of clearings, and appears to avoid forest along rivers where the Malaysian blue-flycatcher (C. turcosus) frequently occurs (2) (4).

Little is known about the biology and ecology of this forest-dwelling bird. Its diet is thought to most likely contain small invertebrates, particularly winged insects (3), which it catches by making short sallies from low exposed perches (2). Usually seen in pairs, large-billed blue-flycatchers have been observed in a breeding condition between February and July, and chicks have been seen in October and November (3).

The future of the large-billed blue-flycatcher is being placed in peril by the catastrophic loss of its forest habitat (3). Between 1985 and 1997, the extent of lowland forest declined by 25 percent in Kalimantan, Borneo, and 30 percent in Sumatra. These devastating losses are primarily the result of industrial-scale logging, an activity that even impacts protected areas (4). Without action, populations of the large-billed blue-flycatcher will continue to decline rapidly (2) (4).

The large-billed blue-flycatcher occurs in several protected areas, including Sepilok Reserve, Sabah; Gunung Mulu National Park, Sarawak; and Kutai National Park, Kalimantan (2), however, as mentioned above, this does not render populations safe from the threat of habitat destruction and degradation. Increasing support for the conservation and management of protected areas in lowland Borneo and Sumatra, and urging governments to reduce logging of lowland forest in the region, are actions that will help ensure the future of the large-billed blue-flycatcher, and the other threatened inhabitants of these forests (3) (4).

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

For further information on the large-billed blue-flycatcher see:

• BirdLife International:
  www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=6567&m=0