This discussion was first published as part of the 2012 Red List update, but remains open for comment to enable reassessment in 2013.
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.
Acosta-Cruz, M. and Mugica-Valdés, L. (2006) Reporte Final – Aves Acuáticas en Cuba. Havana, Cuba: Facultad de Biología, Universidad de la Habana.
No related posts.