Archived 2012-2013 topics: Laysan Duck (Anas laysanensis): downlist to Vulnerable?

This discussion was first published on Dec 1 2010 as part of the 2010-2011 Red List update, but remains open for comment to enable reassessment in 2013. Link to BirdLife species factsheet for Laysan Duck In 2004, Laysan Duck Anas laysanensis was uplisted to Critically Endangered under criterion B1a+c(iv) because new information suggested that its population was undergoing extreme fluctuations within its extremely small range on just one island. However, in 2004 and 2005, 42 individuals were translocated to the two islands of Midway Atoll National Wildlife Refuge; the birds bred successfully in their first year (Reynolds and Klaviter 2006) and the founder population has since increased in size, to an estimated 350 individuals in 2010 (M. Reynolds in litt. 2010), despite being hit by an outbreak of avian botulism in 2008, which killed up to 40-50% of that population (M. Reynolds in litt. 2008). The latest estimate for Laysan put the population there at 503-682 mature individuals (Reynolds and Citta 2007). By the 2011 Red List update, the population will be estimated to have been increasing for at least five years without the occurrence of extreme fluctuations (i.e. a rapid tenfold increase or decrease). Thus it is proposed that this species be downlisted to Vulnerable under criterion D2, as although the species is thought to be increasing, it occupies an AOO of less than 20 km2 and fewer than six locations, and the potential effects of human activities or stochastic events mean it is capable of becoming Critically Endangered or even Extinct in a very short time period. Comments on this proposal would be welcome. Reynolds, M. H. and Citta, J. J. (2007) Postfledging survival of Laysan Ducks. J. Wildl. Manage. 71: 383-388 Reynolds M. and Klavitter J. (2006) Translocation of wild Laysan duck Anas laysanensis to establish a population at Midway Atoll National Wildlife Refuge, United States and US Pacific Possession. Conservation Evidence 3: 6-8 The following letter was received from Michelle Reynolds on 27 February 2011 in reaction to the above topic: Anas laysanensis Reynolds Feb11

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5 Responses to Archived 2012-2013 topics: Laysan Duck (Anas laysanensis): downlist to Vulnerable?

  1. Joe Taylor says:

    Michelle Reynolds submitted the following comments on 18 January 2011:

    I would have been all for downgrading, until the onset of botulism at Midway Atoll in late 2008. The epizootic has re-occurred every year since, and has the potential to wipe out the population -given that every wetland is susceptible and the Laysan ducks do not disperse from the atoll. Management actions have not been effective at stopping the biotoxin, although the labor intensive daily wetland searches and the duck “hospital” is successful in rehabilitating many ducks with partial paralysis . . . The current “insurance” population is very much reliant on intensive management to reduce the magnitude of the botulism outbreaks . . . And given that the entire species range is less than 9 sq. km….and with botulism thriving at higher temps – we are likely to see more of it rather than less of it as time goes on…..

    So yes, there was a successful conservation action, but now there is a new and severe threat.

  2. Jeff Walters says:

    The Laysan Duck continues to qualify as critically endangered under criterion B. Specifically its area of occupancy is (2) less than 10 km2 (it occurs on only two small islands), (a) its area of occupancy is severely fragmented (there is no possibility of dispersal between the two islands) and (c) it undergoes extreme fluctuations in (iv) number of mature individuals (botulism epidemics occur virtually annually on one island, and large fluctuations in population size have been recorded on the other island). With sea level rise posing yet another, new threat, it is in my opinion premature to downgrade this species to vulnerable.

  3. Jeff Walters says:

    The recent tsunami evidences my previous comment that the Laysan Duck remains in an extremely precarious position due to its limited geographic range.

  4. Michelle Reynolds says:

    At the request of the USFWS, I have made two trips to Midway Atoll to help assess the species population status after the March 11 Japan Earthquake generated Tsunami. We have submittted two funding proposals to support new analysis for accurate population estimates (with confidence intervals), and mark additional birds for an updated mark-recapture analysis. Precise estimates are not possible at this time, however initial summaries show approximately 20-30% of the banded adult birds observed before the Tsunami were not observed after the Tsunami.

    The tidal wave hit the Northwestern Hawaiian Islands at night when Laysan ducks are foraging. It partially inundated the two atolls supporting the Laysan duck populations. Midway Atoll and Laysan Island have a mean elevation less than 2.5 m. The Tsunmai overwashed 78% of Eastern Island, about 15% of Sand Island @ Midway Atoll and about 15% of the nesting habitat on Laysan Island. Prior to the Tsunami, two severe winter storms also struck the remote atolls with high winds and extensive flooding (Jan. 12, Feb., 11). The secondary effects of the Tsunami at Midway included a botulism outbreak due to the 100,000+ dead albatross chicks. Also there was saltwater and extensive carcass contamination of freshwater wetlands from the tidal wave (fish, seabirds, debris). Most of the vegetation was denuded (no cover or nesting habitat) after the wave hit Eastern Island which previously supported about 60% of the Midway Atoll population. There were two botulism outbreaks at Midway Atoll in 2011. The first in March after the Tsunmai induced seabird die off, and again during the hottest part of the summer. This is the 4th consecutive summer with a botulism die off. 75 Laysan duck carcasses were collected by the USFWS in 2011 and most suspected or confirmed botulism related mortality.

    On Laysan Island, after the 2011 winter storms and Tsunami, the population experienced complete reproductive failure. Preliminary analysis of population monitoring data at Laysan suggests an adult population decline of 25%.

    Given that the species is restricted to less than 9 km2 with a mean elevation less than 2.5 m, do not disperse between populations, and these isolated populations are less than 200 breeding pairs each, and that the species is subject subject to catastrophic disease outbreaks, vulnerable to tsunamis and sea level rise, severe storms and droughts…seems premature to downlist them until there are more than two populations to offset these risk of random disasters on tiny low islands, and/ effective vaccines are available to prevent botulism die off in small isolated subtropical populations or until a population is established on a larger and/or (predator protected) higher elevation island.

  5. Jeffrey R. Walters says:

    Unfortunately it appears that the impacts of the tsunami and other recent storm events on the Laysan population were greater than originally projected. The latest assessment is that the population has been reduced by 50%. Thanks to the existence of a 2nd population on Midway, the reduction of the Laysan population does not pose the same risk to the continuation of the species that it would have several years ago, but the Midway population continues to be plagued by botulism epidemics and now is experiencing habitat loss. Given all this, it increasingly appears that it will take establishment of a 3rd population on a larger island to truly relieve this species from imminent threat of extinction.

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