Archived 2021 topic: Micronesian Scrubfowl (Megapodius laperouse): Revise global status?

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6 Responses to Archived 2021 topic: Micronesian Scrubfowl (Megapodius laperouse): Revise global status?

  1. Gary J Wiles says:

    I have to seriously question the large number of birds reported for the island of Ascuncion in the Marianas on the 2010 survey, where the population was estimated at 5,714 (95% CI – 3,135-8,821). Given that the island is only 7 sq km in size, this corresponds to a mean density of 816 birds/sq km (95% CI – 448-1,260) across the island. This seems like an impossibly high density, given the numbers reported for the other northern Marianas during the same survey and over the years. This means that your estimate of current population size of the species could easily be a substantail overestimate. As a result, I don’t support reclassifying the species to Near Threatened.

  2. Robert Davis says:

    I agree with Gary that since the proposed downlisting is contingent upon an accurate estimate of the trend and density on the Marianas, more confidence is required on the population size there. I can only speak with experience on the Palau sub-species which is clearly a much smaller population. If this sub-species is elevated to species status in future it would likely be endangered. Our research indicates that populations are potentially impacted by tourism and the impact of rat predation on chicks is also unknown. Given that Kayangel and potentially Peleliu support the majority of the population and that the species shows a strong preference for breeding on near-shore areas, it is vulnerable to a number of threats. Increasing hurricanes and associated storm surges have affected up to 20% of mounds in the Rock Islands and likely therefore also Kayangel and potentially Peleliu. On the basis of my experience in Palau, I do not support the down listing of this species as it remains vulnerable to stochastic and catastrophic events. More confidence on the Marianas population trends and impact of these same threats is warranted prior to any proposed downlisting.

  3. Paul Radley says:

    I agree with Gary that numbers for megapodes on some islands in the Marianas may seem high. However, when looking at the actual survey data, the DISTANCE generated abundance estimates may be a fairly accurate reflection of reality, particularly from the standpoint of distribution of the population. On Asuncion alone 38 stations (separated by 150 meters) along four transects in forested habitat were surveyed via point-transect distance sampling in 2010, both with and without the use of call playback. Distance recorded for megapode detections (both sight and sound) ranged from 0 meters to a little shy of 60 meters, with a mean distance of 18 meters. We counted 151 detections across 34 stations without playback and 174 detections across all 38 stations with playback. This equated to 4.0 birds per station without playback and 4.6 birds per station with playback – i.e., 4.0 to 4.6 megapodes within a mean of 18 meters of the counter at each station. Leaning more conservatively, the lower bound of the 95% CI Gary refers to in his comment (448 birds / square km) comes to 4.48 birds / hectare for the entire island, which is an apt comparison to the number of birds detected per station with playback. As per conversation with Rick Camp (the statistician for the study from which the numbers are derived), modelling detection function in DISTANCE was good and the variance was tight, although there may have been some issues with extrapolation as some areas of suitable megapode habitat could not be accessed and surveyed on Asuncion. Another drawback of DISTANCE is that distribution of detections is considered uniform across the area surveyed, which is of course seldom true in reality because of the distribution in resources. Another thing to consider is that detections were too low on many islands in the archipelago (i.e., Saipan, Alamagan, Pagan and Maug) to directly run DISTANCE analysis. Data therefore were pooled from all islands and results were stratified by island to produce workable estimates for islands that lacked adequate detections. As a result, megapode abundances reported for these islands are likely exaggerated, yielding a total estimate for the archipelago (10,727) that may also be greater than reality.

    Regardless of the potential inaccuracy and / or shortcomings of the statistics (amongst other biological factors), if the results from the 2010 surveys (I note that 2009 is listed as the year the Amidon et al. [2011] surveys were conducted in the Northern Mariana Islands, which is incorrect) are used as an index, 87% of the megapode population in the Mariana archipelago occurs on three islands; Asuncion, Guguan, and Sarigan. These islands are dormant (but very much alive) volcanos that could become active and erupt at most any time. A moderately violent phreatic eruption of Asuncion alone would negatively impact 53% of the megapode population in the Mariana Islands. Another stochastic factor is typhoons, which routinely pass through the Marianas on a yearly basis. With climate change, these storms are predicted to be stronger and more frequent.

    I also strongly agree with Rob and I was involved in much of the research to which he refers. Modelling shows that rising sea levels as a result of climate change will potentially impact the majority of current known megapode nesting areas in the low-lying areas of the Palau archipelago. Although we were not able to show that rats have a serious negative affect on megapodes in Palau, one yet unassessed introduced predator is feral cats. Conversation with biologists with Island Conservation indicate that cats do occur on islands in the Rock Islands Southern Lagoon Conservation Area. The extent of this occurrence and numbers of this serious threat are not known and strongly warrants investigation.

    Given all this information, I feel that down-listing to Near Threatened for this species as a whole is not warranted and would be a mistake. Given its small population size, the lack of surveys for trend determination, and the potential threat of cats and climate change, the Palau population (which may very well be a separate species) should remain listed as Endangered. Owing to the stochastic factors mentioned above, I would likewise suggest the same for the population in the Mariana archipelago, or that it be down-listed no further than Vulnerable if a change needs to be made.

  4. Red List Team (BirdLife International) says:

    Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested by so many people in commenting. The window for consultation is now closed. We will analyse and interpret the new information and post a preliminary decision on this species’s Red List status on this page in early July.

    Thank you once again,
    BirdLife Red List Team

  5. Red List Team (BirdLife International) says:

    Preliminary proposal

    Based on available information, our preliminary proposal for the 2021 Red List would be to adopt the proposed classifications outlined in the initial forum discussion.

    The species must here be assessed globally according to the Criteria; evaluation of the Palau population separately is beyond the scope of this assessment.

    While the species does meet the AOO threshold for VU B2, the number of locations (definition per IUCN Guidelines) exceeds 10, even when considering any of the threats listed in the proposal or forum comments.

    Although there is legitimate concern that some of the population estimates/densities may be unrealistic, even accepting the lowest values (from Radley 2009) yields a largest subpopulation (on Asuncion) comprising more than 1,000 mature individuals, preventing listing as threatened under C2a(i). While volcanic activity, rising sea-levels and typhoons are all credible future threats, they are not yet acting to cause a continuing decline. Hunting and invasive species are similarly not thought to be causing a population decline at an estimable rate.

    Consequently, the available data suggest that the original proposal to list this species as Near Threatened under Criterion B2b(iii) was correct; if the population declines such that the largest subpopulation numbers fewer than 1,000, or the species is recorded declining at an estimable rate, it may warrant uplisting to a threatened category.

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

    The final 2021 Red List categories will be published on the BirdLife and IUCN websites in December 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  6. Red List Team (BirdLife International) says:

    Recommended categorisation to be put forward to IUCN

    The final categorisation for this species has not changed. Micronesian Scrubfowl is recommended to be listed as Near Threatened, approaching the threshold for listing as threatened under Criterion B2b(iii).

    Many thanks for everyone who contributed to the 2021 GTB Forum process. The final 2021 Red List categories will be published on the BirdLife and IUCN websites in December 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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