Palau Ground-dove (Alopecoenas canifrons): Uplist from Near Threatened to Vulnerable?

This discussion was first published as part of the 2017 Red List update. At the time a decision regarding the status of several was pended, but to enable potential reassessment of these species as part of the 2018 Red List update this post remains open and the date of posting has been updated.

Palau Ground-dove (Alopecoenas canifrons) (BirdLife species factsheet) is currently classified as Near Threatened because, although it occurs widely on the Palau Archipelago, it is scarce throughout much of its range and is thought to have a moderately small population.

The species is endemic to Palau where it is found on all the major islands from Babeldaob (very rare) to Angaur, and on many of the small limestone islands south of Koror known as the Rock Islands (where it is more common; Engbring 1988). It prefers limestone islands, inhabiting forest on rocky terrain, where it forages for fallen fruits and seeds in places where deep leaf-litter has accumulated, such as gullies and hollows.

A. canifrons is difficult to locate because of its secretive habits, sparse vocalisations (H. D. Pratt in litt. 1999) and inaccessible habitat and there is a paucity of data on population numbers. An estimate of 500 individuals (Engbring, unpublished data, as cited in Engbring & Pratt 1985) was previously interpreted to refer only to the population on the Rock Islands, but in fact appears to be an estimate for the entire population.

The population was previously estimated by BirdLife to be at the lower end of the band 1,000-2,499 individuals, equating to 667-1,666 mature individuals (rounded to 600-1,700 mature individuals), but may consequently need to be revised downwards.

In 1991 the US Fish and Wildlife Service conducted surveys of the birds of Palau (Engbring 1992). Using a variable circular plot method, they calculated an A. canifrons population density of 0.4 birds /km2 and estimated a population of 164 individuals. However, these findings were based on only nine recorded birds and the survey was therefore unable to provide a meaningful population estimate. Although Engbring acknowledges that A. canifrons is particularly common on the Rock Islands, no individuals were recorded in this location, possibly because these islands were surveyed only by boat and birds were not actively calling at the time.

Another survey of the birds of Palau took place in 2005 (VanderWerf 2007) and followed a similar variable circular plot method to the 1991 survey. An index of relative abundance was calculated for each species and was expressed as the average number of birds per survey station. This survey recorded only four A. canifrons individuals and was again unable to provide a meaningful population estimate, but a relative abundance of 0.006±0.003 birds per survey station was reported (cf. 0.015 birds per station in 1991 [Engbring 1992]). The lower numbers of forest birds recorded in the 2005 survey in comparison with the 1991 survey may have been a result of a drought associated with El Niño weather patterns in 1997-8 (VanderWerf 2007). VanderWerf also reported that A. canifrons was easily observed in a coastal area of Ulong Island not included in the 1991 or 2005 surveys (VanderWerf 2007).

Although the results of the 2005 survey suggested a decline in population density of A. canifrons since 1991, the numbers of birds recorded in these surveys were too low to allow meaningful conclusions and the species has been considered likely to be secure (Sherley 2001). The main threat to A. canifrons is the possibility of introductions of alien species such as rats or brown tree snake (Sherley 2001).

The amount of forest habitat in Palau has declined in recent years and deforestation is predicted to continue (Ketebengang & Gupta 2011). The construction of the Compact Road in 2008 resulted in a loss of 1% of Palau’s forest and has facilitated access to previously inaccessible areas, thereby increasing the likelihood of further development on Babeldoab (Ketebengang & Gupta 2011). However, the Rock Islands, where A. canifrons is reported to be most common, are among the least disturbed areas of Palau and are largely protected as a nature reserve (VanderWerf 2007).

The estimated population of 500 individuals in the 1970s equates to approximately 300 mature individuals, which qualifies the species to be listed as Vulnerable under criterion D1. More recent surveys have suggested a lower population that could potentially be eligible for Endangered status, but the data provided by the surveys was too sparse to support such a conclusion. It is therefore proposed to uplist A. canifrons to Vulnerable.

More recent information on the population size and trend and potential threats to A. canifrons and comments on this proposal are welcomed.

References

Engbring, J. 1988. Field guide to the birds of Palau. Conservation Office and Bureau of Education, Koror, Palau.

Engbring, J. 1992. A 1991 survey of the forest birds of the Republic of Palau. U.S. Fish and Wildlife Service, Honolulu.

Engbring, J., & Pratt, H. D. (1985). Endangered birds in Micronesia: their history, status, and future prospects. Bird conservation, 2, 71-105.

Ketebengang, H., & Gupta, A. (2011). State of Palau’s Birds 2010: A Conservation Guide for Communities and Policymakers. Palau Conservation Society.

Sherley, G. (2001). Issues and options for bird conservation priorities in Micronesia. Priorities and a Draft Avifauna Conservation Strategy for the Pacific Islands Region, 48.

VanderWerf E.A. (2007). 2005 bird surveys in the Republic of Palau. Honolulu, HI: Pacific Rim Conservation.

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One Response to Palau Ground-dove (Alopecoenas canifrons): Uplist from Near Threatened to Vulnerable?

  1. James Westrip (BirdLife) says:

    Preliminary proposals

    Based on available information, our proposal for the 2017 Red List would be to pend the decision on this species and keep this discussion open until 2018, while leaving the current Red List category unchanged in the 2017 update.

    Final 2017 Red List categories will be published on the BirdLife and IUCN websites in early December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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