Data Zone
Justification of Red List category
This crow has recently been rediscovered and is listed as Critically Endangered because it is estimated to have an extremely small population, with the majority of individuals in a single subpopulation, and is inferred to be undergoing a continuing decline owing primarily to on-going habitat loss (BirdLife International 2001). Following further surveys, the species's status may need to be re-evaluated.
Population justification
The species's total population has been estimated at close to 500 individuals, including 50-200 birds in the western Peleng Mountains. Given uncertainty over its population densities and the lack of surveys to confirm its presence in some areas suspected to be occupied by the species, coupled with its tendency to travel in family groups, the number of mature individuals is precautionarily estimated to fall into the band 50-249.
Trend justification
This poorly known species is considered to be in decline owing primarily to habitat loss, although the likely rate of decline has not been quantified.
Corvus unicolor was previously known from two specimens taken on an unspecified island in the Banggai archipelago, immediately east of Sulawesi, Indonesia. A sighting of the species on the western slopes of Peleng in 1991 remained unconfirmed until searches of the island in 2004, 2006 and 2007 confirmed this species survives, although only in forest on the mountain slopes of western Peleng and in small numbers at lower levels in the central isthmus of the island (del Hoyo et al. 2009; Indrawan et al. 2010). Sound recordings were made and two specimens were taken (M. Indrawan in litt. 2007, 2008; Masala et al. 2008). It is thought unlikely that the species is extant on Banggai Island, with only Slender-billed Crows Corvus enca encountered during a 3-day visit in 2005 and an apparent lack of sufficient habitat for C. unicolor (King 2009). Local hunters on Peleng estimate densities of up to 50 birds in a 3- to 4-km radius, thus very rough estimates suggest a global population of up to 500 individuals, with 50-200 birds in the western Peleng Mountains. The montane forests of Buko and Bulagi districts are thought to be the remaining strongholds (M. Indrawan in litt. 2007, 2008; del Hoyo et al. 2009). Interviews with local people strongly suggest that the species is present in mountains in the far west of Peleng, although this region is heavily deforested and it is unlikely to be abundant there (Indrawan et al. 2010).
Relatively little is known of the species's ecology and life history. Sightings have been in remnant hill forest to 900 m on the western side of Peleng and at lower levels in the centre of the island (del Hoyo et al. 2009), with the species distributed principally at 500-900 m (Indrawan et al. 2010). It is reported to have occurred near sea-level in western Peleng around 40 years ago (Indrawan et al. 2010). It occurs in mosaics of forest and cultivation, but not in completely deforested areas, and the species may forage in areas of dry cultivation. Observations suggest that it maintains group territories and probably has extensive home ranges. The species is a branch nester and the nest trees observed so far have been tall (c.12-30 m) forest species, including a Bombaceae, a Calophyllum species, a Canarium species and a Palaquium species; the species probably also nests in Lithocarpus species (Indrawan et al. 2010). Nests are constructed of sparse dry sticks and branches, lined with finer branches and sticks, forming a depressed platform or slightly inverted cone. A given nest tree may contain up to seven nests, although these are probably from different seasons, as the species does not appear to be a colonial nester, with the closest nest trees being 100-200 m apart. Nesting appears to take place during or at the end of the wet season. At least two clutches have been observed so far, of one and three eggs. Following the wet season, juveniles stay with the adults, apparently travelling in family parties. There is one observation of a fledgling being fed arthropods, which may be the species's main food source, and local hunters report that it feeds on winged isopteran termites (Indrawan et al. 2010).
Habitat destruction remains the greatest threat for this rediscovered species. In the past it may have been severely impacted by extensive deforestation, as by 1991 logging had begun in the last remaining areas of primary habitat, which probably led to further encroachment by shifting cultivators as a result of improved access. C. enca appears to have become dominant in more disturbed habitats and may be a competitor (Indrawan et al. 2010). Exploration by mining companies was considered to be a serious potential threat (M. Indrawan in litt. 2007, 2008). However, this has been averted for now due to advocacy work, but it could potential re-emerge as a threat in the future (M. Indrawan in litt. 2016). Although subsistence hunting occurs on Peleng, the species is not sought-after by hunters (Indrawan et al. 2010). The perception by some farmers that the species takes poultry eggs is probably unfounded (Indrawan et al. 2010), but may result in some persecution. Other potential threats are development of tourism and the conversion of of habitat to palm oil plantations, although the latter has been halted by advocacy work (M. Indrawan in litt. 2016).
Conservation Actions Underway
Searches in 2004, 2006 and 2007 successfully rediscovered the species. A long-term engagement project is underway (see Indrawan et al. 2014). A team of local residents are now leading an awareness campaign and promoting the adoption of sustainable agriculture, while hunting of the crow has apparently ceased (M. Indrawan in litt. 2007, 2008). Discussions have taken place with local governments over planned forest protection initiatives (M. Indrawan in litt. 2007, 2008).
39 cm. Small, forest-dwelling crow. All black with pale iris and relatively short tail, heavy black bill and dark feet. The mantle and neck may show a dull brown sheen (Indrawan et al. 2010). The slaty neck and underparts may contrast with the black head, throat, breast and abdomen, and a darker facial mask may be visible. The primaries and trailing edge of the wings are slaty black, and the folded wings potrude beyond the tip of the tail by 1-2 cm. The flight is swift, whistling and direct (Indrawan et al. 2010). Similar spp. Slender-billed Crow C. enca is larger with more massive bill and proportionately longer tail. C. unicolor can superficially resemble Common Cicadabird Coracina tenuirostris when perched (Indrawan et al. 2010). Voice. In a group, birds give a 3-4 note creaking whistle kruik, kruik, kruik, kruik, which lasts 2-3 seconds. This call is occaisionally followed by a melodious two-note whistle, descending and then ascending: whu, weeeeeeee, lasting 2-3 seconds, and sometimes preceded by a metallic tong. Also, a whistled kriuuk . . . kriuuk, lasting 0.8-1.5 seconds, is mostly given in flight. Creaking and trilling notes are also uttered. Juveniles give a repeated soft cawing wree-eek. (Note that Hair-crested Drongo Dicrurus hottentottus is known to imitate the calls of C. unicolor) (Indrawan et al. 2010).
Text account compilers
Symes, A., Taylor, J., Benstead, P., Tobias, J., Westrip, J., Butchart, S., Bird, J., Davidson, P., Harding, M.
Contributors
Indrawan, M.
Recommended citation
BirdLife International (2024) Species factsheet: Banggai Crow Corvus unicolor. Downloaded from
https://datazone.birdlife.org/species/factsheet/banggai-crow-corvus-unicolor on 22/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 22/11/2024.