Corvus unicolor 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Passeriformes Corvidae

Scientific Name: Corvus unicolor (Rothschild & Hartert, 1900)
Common Name(s):
English Banggai Crow
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A., Fishpool, L.D.C., Boesman, P. and Kirwan, G.M. 2016. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions and BirdLife International, Barcelona, Spain and Cambridge, UK.
Identification information: 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).

Assessment Information [top]

Red List Category & Criteria: Critically Endangered C2a(i,ii) ver 3.1
Year Published: 2017
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Indrawan, M.
Facilitator/Compiler(s): Benstead, P., Bird, J., Butchart, S., Davidson, P., Harding, M., Symes, A., Taylor, J., Tobias, J., Westrip, J.
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.

Previously published Red List assessments:

Geographic Range [top]

Range Description: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).

Countries occurrence:
Additional data:
Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:320
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:2-5Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:NoLower elevation limit (metres):600
Upper elevation limit (metres):900
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: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.

Current Population Trend:Decreasing
Additional data:
Number of mature individuals:50-249Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
No. of subpopulations:2Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No
No. of individuals in largest subpopulation:90-94

Habitat and Ecology [top]

Habitat and Ecology: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).

Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):7.3
Movement patterns:Not a Migrant

Threats [top]

Major Threat(s): 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 [top]

Conservation Actions: 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).

Conservation Actions Proposed
Continue to search for the species throughout the archipelago (paying close attention to the use of vocalisations to aid detection) to improve knowledge of its range, distribution, population status, habitat requirements and potential threats. Identify its conservation needs based on results of surveys, and thereby work towards the establishment of appropriately sized and situated protected areas, through community-based forest protection (Indrawan et al. 2010), that support viable populations of this and other threatened species known to occur on the islands. Closely monitor potential mining activity and begin dialogue with mining companies where appropriate. Continue to work with local communities to promote the conservation of this species, concentrating at first on farmers and hunters (Indrawan et al. 2010). On Peleng, monitor C. enca as a potential competitor (Indrawan et al. 2010). Involve local people in research efforts, including studies into the species's diet in order to establish that it is not an egg predator (Indrawan et al. 2010). Encourage sensitive ecotourism that incorporates volunteer work or other contributions to local stakeholders (Indrawan et al. 2010). Support local communities to outline the indigenous territories under forest cover, and aid in forest regeneration (M. Indrawan in litt. 2016). Attempt to limit the impact of tourism on the region (M. Indrawan in litt. 2016).

Errata [top]

Errata reason: Minor change to Threats Information text.

Amended [top]

Amended reason: Edited Conservation Actions, Population Trend Justification and Threats Information text. Added a threat and made some amendments to Actions Needed. Added a reference, and altered the field info for another reference. Also added a Facilitator/Compiler.

Citation: BirdLife International. 2017. Corvus unicolor (errata version published in 2018) (amended version of 2016 assessment). The IUCN Red List of Threatened Species 2017: e.T22705953A125525069. . Downloaded on 16 August 2018.
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