West Indian Whistling-duck (Dendrocygna arborea): request for information

This discussion was first published as part of the 2012 Red List update, but remains open for comment to enable reassessment in 2014.

BirdLife species factsheet for West Indian Whistling-duck

West Indian Whistling-duck Dendrocygna arborea is currently classified as Vulnerable under criterion B2a+b(i,ii,iii,iv,v) because it was thought to have a small Area of Occupancy (AOO) considered to be severely fragmented and declining in extent and habitat quality. The AOO is analogous to the area of suitable habitat occupied by the species, and for most taxa it is measured using 2 × 2 km grid cells. An up-to-date estimate of the species’s AOO is apparently not available, thus criterion B2 (for species with a small AOO which is declining or fluctuating) cannot be safely applied in this case.

Surveys carried out in Cuba – the most significant part of the species’s range both in size and population numbers – have shown the species to be more widespread on the main island and adjacent offshore islands than was previously thought. This has led to a significant increase in its estimated Extent of Occurrence (range encompassing all records) to c. 102,000 km2. The population in Cuba is now estimated to number c.14,000 individuals, based on a survey of hunters (Acosta-Cruz and Mugica-Valdés 2006), which did not cover all known sites and is thus suspected to have underestimated numbers (L. Mugica in litt. 2011). Another c.6,000 individuals are roughly estimated to occur elsewhere in its range (D. Wege in litt. 2007), giving a very rough global population estimate of c.20,000 individuals. The species now appears to be increasing in parts of its range, owing to successful conservation efforts. Despite this, the threats of wetland conversion and degradation are on-going (L. Sorenson in litt. 2009), making judgments of the overall population trend very difficult.

Present knowledge suggests that the species does not meet the thresholds for Vulnerable under any of the IUCN Red List criteria and may warrant downlisting. However, the species would remain listed as Vulnerable if evidence were to suggest that it has declined or will decline at a rate of at least 30% over three generations (estimated by BirdLife to be 16 years in this species) (criterion A), or that it has an AOO of less than 2,000 km2 with evidence of declines in the range or population (criterion B2), or that it has a total population of fewer than 10,000 mature individuals, with all individuals in one subpopulation or all subpopulations numbering fewer than 1,000 individuals, and evidence of a continuing decline (criterion C). If evidence suggests that the species approaches (but does not meet) the thresholds for Vulnerable under at least one of these criteria, it may qualify as Near Threatened. Further information on this species is requested.

References:

Acosta-Cruz, M. and Mugica-Valdés, L. (2006) Reporte Final – Aves Acuáticas en Cuba. Havana, Cuba: Facultad de Biología, Universidad de la Habana.

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7 Responses to West Indian Whistling-duck (Dendrocygna arborea): request for information

  1. The Society for the Conservation and Study of Caribbean Birds (SCSCB) West Indian Whistling Duck and Wetlands (WIWD) Working Group advises that it would be premature to down-list the WIWD from Vulnerable to Near Threatened status at this time. We have consulted with bird conservation interests from across the Caribbean and there is consensus that down-listing would have a serious negative impact on conservation efforts across the region and could reverse the fragile progress that has been made over the last 10 years.

    We understand that the main reason for the recommended change in status is the estimate of the Cuban population in excess of 14,000 individuals. This raises several important points. Firstly, and most importantly, we note that the estimate is based on reports from hunters who have no training in bird monitoring, bird identification or science. Our own experience of reports from hunters suggests that they are likely to be optimistic for many reasons. We consider that the IUCN should base its decisions on properly designed, scientifically rigorous, peer-reviewed, published data with estimates of reliability and margins of error. To do otherwise is to undermine efforts to promote proper science.

    We respect Lourdes Mujica’s efforts to work with the National Federation Sport Hunting organization in Cuba to educate them and also gather information from them on their observations of different groups of birds in the field. We think the population estimates they have generated are a valuable contribution, but it is not a sufficient basis for changing the status of this species.

    We do know that WIWDs in Cuba often occur in the same habitats as the Fulvous Whistling Duck (Dendrocygna bicolor), which vastly outnumbers it. We consider that there is a large risk that the population on Cuba has been greatly over-estimated, possibly due to confusion of the various whistling-duck species.

    Secondly, we note that in the absence of life history information, all we have are estimates of the number of individuals, and there is no way of extrapolating the number of breeding adults (as stipulated in the IUCN definition).

    Thirdly, we would also argue that the IUCN population criterion is difficult to apply in the case of the WIWD because of the imbalance of population numbers between Cuba and the other islands. Whatever the numbers might be in Cuba, there is no doubt that populations on all other islands are small and highly vulnerable to habitat loss and hunting. Good data are still lacking from most countries, and populations throughout the species’ range (with the exception of Cuba) are small and fragmented. The margins of error for population “guesstimates” in each country are unknown and probably quite large, and there is very little information available about dispersal, reproductive success, survival and productivity—information badly needed to assess demographic factors associated with population trend. Changing the status at this point means that there is a serious risk that sub-populations could be lost.

    There is good evidence from long-term monitoring efforts that conservation efforts are working, e.g., WIWD populations in Antigua have increased (J. Prosper in prep.), and anecdotal evidence from other countries/ islands (e.g., Jamaica, Cayman Islands, Cuba) indicates that populations are stable or increasing. In addition, first nesting of WIWDs in Guadeloupe was documented in 2008 (Levesque and Sorenson, in review), representing a range expansion of the species (most likely due to an increasing population in nearby Antigua). But these gains are fragile and could easily be reversed if, as is likely, down-listing leads to increased pressure for legal hunting (as might well happen in Jamaica, A. Sutton, pers. comm.).

    The WIWD Working Group (WG) of the SCSCB has been working to conserve this threatened regional endemic and the wetland habitats upon which it depends through a region-wide public education and awareness program—the WIWD and Wetlands Conservation Project (Sorenson et al. 2004, 2005). The educational materials that have been produced and associated workshops have helped raise the profile of the duck. With increased awareness about the status of the duck and the importance and value of local wetlands, hunting has declined on most islands and many citizens and local groups have worked to successfully save some wetlands from development and restore them.

    The main threats to the species’ survival—destruction and degradation of wetland habitats, introduced predators (e.g., mongoose, raccoons, rats, feral cats) that eat ducklings and/or eggs, and unregulated hunting and poaching (Staus 2005)— have not been reduced to the point where we can be confident that the species’ survival is assured. Wetlands throughout the Caribbean (especially coastal habitats) are under constant threat of development and they continue to be destroyed, degraded and mismanaged.

    Climate change is likely to exacerbate existing stresses on wetland habitats and negatively impact the birds that rely on those habitats. Climate models for the region predict increased frequency and severity of drought, storms, and hurricanes with an overall drying trend in the coming century (Neelin et al. 2006). Effects of hurricanes on waterbirds are well known: they suffer higher mortality and reduced reproductive success from both direct and indirect effects (Wunderle 2005). An overall drying trend means that wetlands of all types—salt, brackish and freshwater—are at risk of drying up, which will result in further loss of habitat. Projected rises in sea level may further reduce the extent of remaining mangrove habitat, vitally important for the species. These threats and changes will continue to present challenges to the future survival of WIWDs and other aquatic birds.

    Although legal and illegal hunting of the species has declined due to hunter outreach by WIWD WG and SCSCB members and partners, there are periodic reports of poaching in known habitats of the bird (including as recently as 29 January 2012 in Black River Upper Morass, Jamaica) and the species is still legally hunted on some islands (e.g., Guadeloupe). Constant vigilance to monitor illegal hunting, and continued efforts to educate decision-makers and hunters, and to have the species placed on protected lists are needed.

    The presence of the duck and its global status has been a major incentive for protecting wetlands and the duck in many countries. A number of wetlands have been designated as IBAs because of local WIWD populations and their IBA status is a valuable tool for countering proposed developments. Down-listing the status at this time will not be helpful.

    In summary, we think it is unwise to change the listing for the species. We query the validity of the data on which the population estimate has been based.

    We do not believe it is prudent to change the status of a species on the basis of unverified non-scientific information, and strongly recommend that before any decision is taken, IUCN should help the SCSCB to generate the necessary scientific data by helping us to raise the funds needed to implement our on-going initiatives to stimulate research and monitoring [1] and to determine WIWD population sizes and trends in each country throughout its range. We also need support to generate greater knowledge of the species breeding biology, movements and habitat needs so that we can better model the population trends and assess the effectiveness of our conservation initiatives.

    Literature Cited

    Levesque, A. and L.G. Sorenson, in review. First record of a West Indian Whistling-Duck
    (Dendrocygna arborea) nesting in Guadeloupe. Journal of Caribbean Ornithology.

    Neelin, J.D., M. Munnich, H. Su, J.E. Meyerson, and C.E. Holloway. 2006. Proceedings of the Natural Academy Scientists

    Sorenson, L.G. 1992. Variable mating system of a sedentary tropical duck: the white-cheeked pintail (Anas bahamensis bahamensis). Auk 109: 277-292.

    Sorenson, L.G., Bradley, P.E. and M. Haynes Sutton. 2004. The West Indian whistling-duck and wetlands conservation project: a model for species and wetlands conservation and education. The Journal of Caribbean Ornithology, Special Issue pp. 72-80.

    Sorenson, L.G. Bradley, P., Mugica, L., and K. Wallace. 2005. West Indian whistling-duck and wetlands conservation project: symposium report and project news. The Journal of Caribbean Ornithology 18: 102-105.

    Staus, N. 2005. West Indian Whistling-duck Dendrocygna arborea (species account). in Bird Families of the World: Ducks, Geese, Swans. Edited by J. Kear, Oxford University Press. Vol. 1: 197-199

    Wunderle, J. 2005. Hurricanes and the fate of Caribbean Birds—What do we know, what do we need to know, who is vulnerable, how can we prepare, what can we do, and what are the management options? J. Carib. Ornithol. 18:94-96.

    [1] As part of SCSCB’s Caribbean Waterbird Census (CWC) (http://conserveonline.org/workspaces/cwc) and BirdWatch Monitoring Programs, we have recently developed a monitoring manual for the WIWD and we hope to raise funds to support monitoring and further study of the species. We will encourage in-country partners countries to monitor WIWDs on at least an annual basis. We expect to have better knowledge of the species status through these efforts in the future.

  2. Lisa’s comments are very interesting and we classified the WIWD as “ENDANGERED” in Guadeloupe using IUCN criterion. Downlisted the species will also make the things much more difficult in Guadeloupe with hunters, actually in Guadeloupe the species is not on the protected list nor on the game list because the arrival of the bird is recent there. So I would vote to maintain the species as “VU”. I agree that census by hunters are not always reliable…

  3. I support all of Sorenson’s comments. Like Cuba there are no recent population estimates in the Cayman Islands from c. 1500-1800 (Bradley et al 2006). The population has fallen dramatically in Little Cayman following the most recent hurricanes in 2007 and 2008, and in three successive years the wetlands have dried down early (by late February-early March) from 350 in 2006-under 50. In Cayman Brac there is a small population under 30 in the reduced wetlands ( often fed by a landowner). In Grand Cayman my assessment is as follows: There are ducks (20–50) at each of 3 privately owned small ponds and 300-500 at a large privately owned lake and fed by owner.Ducks are frequently seen in pairs at South Sound. The large concentrations in the northern wetlands appear to have dispersed to the private areas. In the Central Mangrove Wetland development has removed much of the black mangrove where the ducks nested and numbers are fewer in the buttonwood wetlands ot the east. Ducks are more visible due to reduced hunting pressures, conservation education and feeding stations but wild distribution has been severly reduced by development and predation by packs of dogs. The situation in the islands is not going to improve as new major development projects are now starting in Grand Cayman and the wetlands are included. In ten years WIWD will be confined to land protected by the National Trust (which now protects over 5% of the land area of the CI) on in private ponds. The WIWd should stay where it is on the list.
    Bradley et al. IN IBAs in the UKOTs (BirdLife 2006),

  4. Further comment: the IBA publication went to press before the 2004 hurricane demolished Grand Cayman, flattening wetland forests in the Central Mangrove Wetland and opening areas up for development and marl extraction on the black mangrove edge. The WIWD population was severly impacted and starving birds came into gardens to be fed.

  5. Andy Symes says:

    Preliminary proposals

    Based on available information, our preliminary proposal for the 2014 Red List is to pend the decision on West Indian Whistling-duck Dendrocygna arborea and keep this discussion open until early 2015, while leaving the current Red List category unchanged in the 2014 update.

    There is now a period for further comments until the final deadline of 31 March, after which recommended categorisations will be put forward to IUCN.

    The final Red List categories will be published on the BirdLife and IUCN websites in mid-2014, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  6. We are fighting new threats to wetlands and hear of wetlands that have been lost to development in the Caribbean all too often. The latest threat to WIWD habitat in the region is the development of a transshipment port and logistics hub in Portland Bight Protected Area, Jamaica, an IBA, KBA, Ramsar site and protected area (www.savegoatislands.org). WIWDs are known to use this area but many acres of mangroves will be destroyed by this development, reducing available habitat for the duck in Jamaica.

    The comments of the WIWD Working Group of BirdsCaribbean (formerly the Society for the Conservation and Study of Caribbean Birds) from Jan. 31, 2012 are still valid. Downgrading the duck from its Vulnerable status would not be wise for all the reasons outlined in our comments, plus it will further weaken our ability to protect wetlands throughout the species’ range, where it’s survival is precarious due to habitat loss, invasive species and occasional poaching and hunting.

  7. Ann Sutton says:

    I support Lisa Sorenson/WIWD’s comments. There is an urgent need for a reassessment of the status of WIWDs in Jamaica, which previously supported one of the larger populations outside Cuba because ad hoc observations suggest that numbers of ducks are declining at several of the former strongholds of the species (including Negril and Black River). This may be related to an apparent increase in illegal hunting of ducks in 2014. In addition, as Lisa mentioned above, habitat destruction is an increasing threat. The impacts of the port development at Falmouth on WIWDs have not been assessed. The proposed transshipment port at Goat Islands, in the Portland Bight Protected Area, would as Lisa mentions above, destroy and fragment some of the best remaining habitat for the species. Similar port developments are being proposed across the region, and it is likely that the threat of habitat loss is also increasing on many islands.

    Changing the status of this species at this time would send the wrong message to our decision-makers, and weaken the position of many conservationists inside and outside government departments.

    I think it is important that decisions of this sort should be made based on scientific studies that meet agreed standards. The survey of hunters in Cuba produced a lot of useful information but it was not designed for this purpose.

    Finally, I think it is important to consider the importance of being able to demonstrate that improvements in status are stable (e.g. over a period of at least 10 years), and that if possible populations are stable or increasing across the range of the species, on multiple islands.

    I think that changing the status of WIWDs at this time would be a serious mistake.

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