This discussion was first published as part of the 2013 Red List update, but remains open for comment to enable reassessment in 2014.
Micronesian Imperial-pigeon Ducula oceanica occurs in the Micronesian islands of Palau, Yap, Chuuk, Pohnpei and Kosrae (Federated States of Micronesia), including many small offshore islands. It is probably extinct on Kiribati and Nauru, and many or all of the Marshall Islands (Gibbs et al. 2001). It is currently listed as Near Threatened under criteria A2bcd+3bcd+4bcd because, although still reasonably abundant on some islands in its range, it is in moderately rapid decline owing to hunting for food and habitat loss, and thus approaches the thresholds for Vulnerable. However, recent surveys suggest the species may be declining more rapidly than this on some islands and thus it may warrant uplisting.
There were estimated to be 13,718 birds on Palau in 1991 (Engbring 1992), with 572 on Yap, 51 on Chuuk, 822 on Pohnpei and 7,474 on Kosrae in 1983-1984 (Engbring 1990), and c.80 in the Marshall Islands in 2011 (M. O’Brien in litt. 2011), following recovery efforts. Numbers on Pohnpei are known to have declined by about 70% between 1983 and 1994 (Buden 2000). The population on Kosrae is inferred to have declined less severely due to the lower rate of forest loss and smaller human population on that island. In 2005, the Palau Conservation Society and the US Fish and Wildlife Service repeated the National Bird Survey that was conducted in 1991. The resulting data were not analysed in the same way as those from the 1991 survey, and so are not comparable. However, relative abundance (birds/station) was compared between the two surveys, showing that abundance decreased by c.40% between 1991 and 2005. If this decline in relative abundance is applied to the 1991 population estimate, then the estimated population on Palau in 2005 is c.8,175. In addition, there was a marked decrease in the number of birds observed at monitoring stations between 2005 and 2010 (Olsen and Eberdong 2011), indicating a possible rapid decline in the population and/or a possible contraction in range. The 2005 survey also showed that the species was most common in remote areas far from human populations, and less common on transects near towns and roads, suggesting that hunting pressure is responsible for the decline.
If the evidence that the population of this species is declining at a more rapid rate is confirmed, and there is an estimated reduction of ≥30% over three generations (c.20 years in this species [BirdLife International, unpubl. data]) in the past and/or projected in the future, this species would warrant uplisting to Vulnerable under criteria A2bcd+3bcd+4bcd of the IUCN Red List.
Further information is requested on this species’s population size and trends, and additional comments on the proposed uplisting are welcome.
Buden, D. W. (2000) A comparison of 1983 and 1994 bird surveys of Pohnpei, Federated States of Micronesia. Wilson Bulletin 112: 403-410.
Engbring, J. (1992) A 1991 survey of the forest birds of the Republic of Palau. U.S. Fish and Wildlife Service, Honolulu.
Engbring, J., Ramsey, F. L. and Wildman, V. J. (1990) Micronesian forest bird surveys, the Federated States: Pohnpei, Kosrae, Chuuk, and Yap. U.S. Fish and Wildlife Service, Honolulu.
Gibbs, D., Barnes, E. and Cox, J. (2001) Pigeons and doves: a guide to the pigeons and doves of the world. Robertsbridge, UK: Pica Press.
Olsen A.R. and Eberdong M. (2011). State of Palau’s birds, 2010. Koror, Palau: Belau National Museum.
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