Initial deadline for comments: 31 January 2012 [note that this has been moved back by about two months].
River Tern Sterna aurantia inhabits rivers and freshwater lakes in the Indian Subcontinent, South-East Asia and southern China, also occurring rarely on estuaries, and breeds on sandy islands (del Hoyo et al. 1996). This species is listed as being of Least Concern on the basis that it is not thought to approach the thresholds for Vulnerable under any of the IUCN criteria.
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence of less than 20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (at least a 30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (fewer than 10,000 mature individuals with a continuing decline estimated to be at least 10% over ten years or three generations, or with a specified population structure).
Despite its current Red List category, the present status of this widespread species is poorly understood. Nesting areas are vulnerable to flooding, predation and disturbance (del Hoyo et al. 1996). It has reportedly declined in abundance in Thailand, where it is now considered very rare (del Hoyo et al.1996). The species has also declined in Laos since the early 20th century, probably owing mainly to excessive human disturbance on sandbars (Thewlis et al. 1998). The multitude of hydroelectric dam projects completed, underway or planned in South-East Asia (e.g. Thewlis et al. 1998) may also threaten the species through changes to flow regime and flooding of nest-sites. In contrast, the species is now more regular in southern India than was once thought.
Further information on this species is requested, with particular emphasis on population trends and details of potential threats. If the available evidence suggests that the overall rate of decline has approached 30% (typically 20-29%) over the past three generations, estimated by BirdLife to be c.30 years in this species, then it may be eligible for uplisting to Near Threatened under the A criterion. If evidence supports the suspicion of a decline of at least 30% over the past 30 years the species could qualify for uplisting to Vulnerable.
del Hoyo, J., Elliott, A. and Sargatal, J. (1996) Handbook of the birds of the world, Vol 3: Hoatzin to Auks. Barcelona, Spain: Lynx Edicions.
Thewlis, R. M., Timmins, R. J., Evans, T. D. and Duckworth, J. W. (1998) The conservation status of birds in Laos: a review of key species. Bird Conserv. Int. 8 (Suppl.): 1-159.