Justification of Red List Category
Although still reasonably abundant on some islands in its range, this species is much prized for food and is consequently becoming increasingly scarce, it is also declining owing to habitat loss; it is therefore classified as Near Threatened; it almost meets the requirements for listing as threatened under criterion A2bcd+3bcd+4bcd.
The global population size has not been quantified, but the species is described as fairly common on Palau, Yap Pohnpei and Kosrae and rare to extinct on Chuuk and some of the Marshall islands (Gibbs et al. 2001).
There are few data on which to calculate a trend; however, the species is hunted through much of its range and habitat loss, which has been dramatic in certain places, is suspected to be causing a slow to moderate population decline. Recent surveys suggest the species may be declining rapidly on some islands, and further analysis of survey data is required to confirm this.
This species occurs in the Micronesian islands of Palau, Yap, Chuuk, Pohnpei and Kosrae (Federated States of Micronesia), including many small offshore islands. The species was still extant on Nauru in 2006-2007 (Buden 2008). It is probably extinct on Kiribati and many or all of the Marshall Islands (Gibbs et al. 2001). There were estimated to be 13,718 birds on Palau in 1991 (Engbring 1992), and 572 on Yap, 51 on Chuuk, 822 on Pohnpei, 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. The population on Nauru was estimated at 75-100 individuals in 2006-2007 (Buden 2008). 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 2010). This indicates a possible rapid decline in the population and/ or a possible restriction in range. The 2005 survey 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. Further analysis of the data is needed to determine the species trend and to identify any potential range restrictions in Palau.
It is a forest species, found predominantly in the mountains of Pohnpei and Kosrae, but widespread where not hunted, including secondary forest, beach forest and mangroves (Engbring 1990). It feeds on a variety of fruits and large fleshy seeds (Baptista et al. 1997). It is thought to breed year-round.
The main threat is hunting for food and especially as a cultural food item; this has continued on Palau despite a fire-arms ban (Engbring 1990, Buden 2000, E. Matthews pers. comm. 2007, A. Gupta in litt. 2011) and has been suggested to be driving the decline of the species on Palau (Ketebengang and Gupta 2011) and Nauru (Buden 2008). Nestlings are occasionally taken for raising in captivity (VanderWerf 2007). Ongoing forest clearance for agriculture is another concern, upland forest on Pohnpei has declined by about two thirds between 1975-1995 (Trustrum 1996), although deforestation rates on other islands have not been so intense.
Conservation and Research Actions Underway
In 1991 and 2005, the Palau Conservation Society and the US Fish and Wildlife Service conducted the National Bird Survey which involved surveying the species's abundance on Palau. In the Marshall Islands, a recovery programme for the species has been launched by the Marshall Islands Conservation Society, with numbers in the Majuro Atoll now reaching up to c.80 individuals on a complex of 27 islets (M. O'Brien in litt. 2011).
Conservation and Research Actions Proposed
Conduct surveys to assess its total population size and distribution. Monitor population trends through regular surveys. Monitor rates of habitat loss and degradation. Monitor levels of hunting pressure. Protect significant habitat, particularly on Kosrae where numbers are particularly high. Enforce the fire-arms ban on Palau. Prevent hunting of the species.
Text account compilers
Derhé, M., Dutson, G., Mahood, S., O'Brien, A. & Ashpole, J
Matthews, E., O'Brien, M. & Gupta, A.
BirdLife International (2019) Species factsheet: Ducula oceanica. Downloaded from http://www.birdlife.org on 21/10/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/10/2019.