Archived 2018 topic: 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 its status was pended, but to enable potential reassessment of the species as part of the 2018 Red List update this post was kept open. A decision has now been made and this topic is now closed.

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 An estimate of 500 individuals (Engbring, unpublished data, as cited in Engbring & Pratt 1985) was previously interpreted to refer only to the population on the Rock Islands, but in fact appears to be an estimate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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5 Responses to Archived 2018 topic: 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.

  2. Hannah Wheatley (BirdLife) says:

    The following comment has been received from Glenn McKinlay via email:

    Ground doves would appear to have recently disappeared, or become very scarce at Ulong Beach, which was the most reliable site for visiting birders.
    I have not seen one there this year in 4 visits, whereas up to mid 2017 I could find them with near 100% reliability. In 2005 Venderwerf stated for that site “ground-doves were found to be fairly common, or at least easily observed”.
    This change follows clearing of undergrowth vegetation, trail clearing and increased human foot traffic. Also rats are abundant.

    Whilst this is likely to be a site specific decline, it would be difficult to detect a generalised population decline to be detected. Cats are present in some rock islands, Babeldoab, Carp island, and presumably Peleliu. Rats are also likely to have a negative impact on ground doves.

    Results from Koror State’s recently initiated monthly station counts in the rock islands should be consulted.

  3. Hannah Wheatley (BirdLife) says:

    The following comment has been received from Daisuke Horii via email:

    We have started our monitoring project since October 2017. We conduct it every month. More than 60 site-days have been undertaken so far. There are total 14 sites in the Rock Island Southern Lagoon (RISL). The 7 sites out of them are monitored monthly, and the other 7 sites were monitored every 6 month (March and September). Each site has 1-3 monitoring stations. We count birds for 15 minutes at each of the stations. Exceptionally, Ngemelis has a transect line.

    We have not recorded any Ground Dove in RISL through our monitoring project since October 2017.

    However, if you check eBird, three sights were reported by other birders in 2017-2018 (in Ngchus in May 2017, in Ulong in January 2018 and Carp Island on June 2018).

    N.B. This comment was edited on 18th July 2018. The comment originally stated that during the monitoring project, the Palau Ground Dove was recorded only once, which was in Ngemelis on June 13, 2018. This record was subsequently found to be an error, so the comment has been amended accordingly.

  4. Hannah Wheatley (BirdLife) says:

    Preliminary proposals

    Following review of comments received in response to this topic, our preliminary proposal for the 2018 Red List would be to list this species as Endangered under Criterion C2a(i).

    The results of recent surveys in the Rock Islands, together with those of previous surveys as described in the above topic, suggest that the population size is likely to fall below 1,000 mature individuals. The species is distributed across the islands of Palau in subpopulations that are likely to number fewer than 250 mature individuals each. There is also evidence that the species is undergoing a continuing decline. Whilst the species has long been considered to be rare, recent sightings have been extremely sparse and the species appears to have disappeared from a site where it was previously reliably recorded. Cats and rats are present in parts of the species’s range and are thought likely to impact on the population. Further evidence is provided by an analysis of forest loss from 2000-2012 (Tracewski et al. 2016), which found that forest had been lost across the species’s range at a rate equivalent to 4% across three generations.

    There is now a period for further comments until the final deadline in mid-July, after which the recommended categorisations will be put forward to IUCN.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from the initial proposal.
    The final 2018 Red List categories will be published on the BirdLife and IUCN websites in November, following further checking of information relevant to the assessments by both BirdLife and IUCN.

    Reference

    Tracewski, Ł.; Butchart, S. H. M.; Di Marco, M.; Ficetola, G. F.; Rondinini, C.; Symes, A.; Wheatley, H.; Beresford, A. E.; Buchanan, G. M. 2016. Toward quantification of the impact of 21st-century deforestation on the extinction risk of terrestrial vertebrates. Conservation Biology 30: 1070-1079.

  5. I have to agree with the proposal to uplift this species to Endangered. Having worked in Palau since 2012 and mostly on the Rock Islands where this species occurs, we have very few records. As mentioned by Glenn McKinlay, they could be reliably found on Ulong until recently and we have also captured one there in a mist-net during studies on the Micronesian Megapode. They are clearly a very cryptic species, however so could potentially be overlooked. In 2012 I ran a workshop to assess the conservation status of Palau’s birds. All participants that were experts on Palau’s birds, agreed that this species was probably more threatened than it’s current listing suggested.

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