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| 2010 IUCN Red List Category (as evaluated by BirdLife International - the official Red List Authority for birds for IUCN): Critically Endangered Justification This species qualifies as Critically Endangered because surveys have shown that it is declining extremely rapidly. It now has an extremely small population and is effectively confined to just one island where multiple factors are driving the decline. Urgent conservation measures are required to ensure that this species does not become extinct.
Family/Sub-family Corvidae Species name author Reichenow, 1885 Taxonomic source(s) Sibley and Monroe (1990, 1993) Identification 38 cm. Medium-sized crow. All black, with slight gloss. Similar spp. Black Drongo Dicrurus macrocercus much smaller and slimmer with red eyes and forked tail. Micronesian Starling Aplonis opaca similarly shaped, but much smaller with golden-yellow eyes. Voice Loud scream kaaa-ah. Hints Shyer than most crows, often hiding in the forest.
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Population estimate | Population trend | Range estimate (breeding/resident) | Country endemic? | 50-249 | decreasing | 220 km2 | No |
Range & population Corvus kubaryi inhabits Guam (to USA) and Rota in the Northern Marianas Islands (to USA). On Guam, it was formerly common but, since the 1960s, declined in numbers and area inhabited3 with an estimated 350 birds in 19811, less than 40 in 19953, and seven in 1999. Following introduction of birds from Rota the population rose to 16 in 200110, but has since declined to four (all males)15. On Rota, it was thought to be stable, estimated at 1,318 birds in 19822, but has since declined to 592 in 19953, and then to 234 in 19986,14; in 2007 there were c.50 confirmed pairs and a few more suspected15, and the population in 2008 stands at around 85 pairs16. Three birds are held in captivity7. Surveys on Rota between 1982 and 2004 indicated a decline of 93%16.
| Ecology: It inhabits mature and second growth forest and coastal strand vegetation5 but probably only nests in native forest6. It forages in the forest canopy, understorey and occasionally on the forest floor for seeds, fruit, arthropods and lizards5.
| Threats On Guam, its decline was due to predation by the introduced brown tree snake Boiga irregularis and, despite protection of nest-sites by electrical tree barriers, it is now effectively extinct there8. On Rota, recent typhoons have devastated forest habitat and forest has been cleared for homestead development, resort and golf-course construction and agricultural settlement; actions which are often accompanied by direct persecution (shooting)4,8,10,14. Additional threats include nest-predation/disturbance by introduced rats Rattus spp. and monitor lizard Varanus indicus, competition with introduced Black Drongo Dicrurus macrocercus and disease6,16. Brown tree snake is not yet established on Rota, but if a snake population becomes established an even more serious decline is likely. Having a distribution on relatively low-lying islands, this species is potentially susceptible to climate change through sea-level rise and shifts in suitable climatic conditions17.
| | Conservation measures underway On Guam, a National Wildlife Refuge was established in 1993 to preserve remaining forest9, and birds are being translocated from Rota in an effort to maintain the wild population on the island. A 40 ha snake-free area created on North-west field is available for the introduction of crows, and an adjacent larger area is being readied for the translocation of Rota crows12. A predation control experiment will soon be starting on Rota, which may include demographic work in the future. A grant has been obtained for a Habitat Conservation Plan for Rota's Agricultural Homesteads, which will increase the amount of land in protected areas13. Biological control for the brown tree snake is also being investigated12. On Rota, life history studies are currently being conducted and there are proposals to protect vital tracts of forest under a Habitat Conservation Plan8,10.
| | Conservation measures proposed Implement stringent measures to prevent the spread of B. irregularis from Guam to Rota8,10. Continue research including study of population biology and health of marked birds6,8. Conduct annual censuses using standardised methodology6,8,10. Continue nest protection and increase trapping of Rattus spp. and Varanus indicus in adjacent areas8. Begin control of Dicrurus macrocercus. Facilitate the enactment of the proposed Habitat Conservation Plan6,8,10. Conduct a public education programme to reduce persecution8. Introduce more stringent controls for construction projects.
| References 1. Engbring and Pratt (1985). 2. Engbring et al. (1982). 3. Fancy et al. (1999). 4. J. Lepson in litt. (1999). 5. Michael (1987). 6. Morton et al. (1999). 7. J. Morton in litt. (2000). 8. National Research Council (1997). 9. Wiles et al. (1995). 10. G. Wiles in litt. (1999). 11. A. Saunders in litt. (2003). 12. Beck and Savidge (2000). 13. T. de Cruz in litt. (2003). 14. Plentovich et al (2005). 15. G. Rodda in litt. (2007). 16. Amar et al. (2008). 17. BirdLife International (unpublished data).
| Text account compilers Rob Calvert (BirdLife International), Simon Mahood (BirdLife International), Andrew O'Brien (BirdLife International), Sue Shutes (BirdLife International), Alison Stattersfield (BirdLife International), Andy Symes (BirdLife International) | Contributors Rick Camp (US Geological Survey), Tina de Cruz (University of Otago), Jaan Lepson, John Morton (US Fish & Wildlife Service), Gordon Rodda (US Fish & Wildlife Service), Alan Saunders (Department of Conservation), G. Wiles | IUCN Red List evaluators Stuart Butchart (BirdLife International), Rob Calvert (BirdLife International), Andy Symes (BirdLife International) |
| Recommended citation BirdLife International (2010) Species factsheet: Corvus kubaryi. Downloaded from http://www.birdlife.org on 3/9/2010 | This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List. To provide new information to update this factsheet or to correct any errors, please email BirdLife To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums |
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