Lesser Adjutant Leptoptilos javanicus has an extensive range across South and South-East Asia (BirdLife International 2001). It is currently listed as Vulnerable under criterion A2cd+3cd+4cd of the IUCN Red List because its population was suspected to be rapidly declining at a rate of ≥30% over three generations (48 years in this species), in line with increasing levels of felling of colony nest trees, drainage and conversion of wetland feeding areas, agricultural intensification, pesticide use, disturbance and large-scale development in coastal areas. The most serious threat, however, is the persistent and unregulated harvesting of eggs and chicks from colonies.
However, some populations at least seem to be relatively stable, e.g. numbers in the Matang Mangrove Forest, Malaysia have remained relatively constant for 20 years (Li et al. 2007). The current population estimate is 5,000 birds; however, an increase in survey effort across much of the region has revised many national totals upwards. Analysis of Cambodian records estimated a national population of c.1,870 pairs (Bird et al. 2007); precautionary interpretation of this figure suggested the previous national estimate of 1,000 individuals should be revised upwards considerably to 2,500-4,000 individuals. The species is said to have definitely benefited from conservation action in Cambodia, ensuring colony protection from egg and chick harvesting and its population could easily be 50% to 100% larger than the current estimate (Goes in prep. 2012). Therefore, overall the global population may be considerably larger than previous estimates (approximately 4,300 – 5,300 mature individuals or more). In addition, calculating the rate of decline for a widespread species which occurs in relatively low numbers is difficult (S. Mahood in litt. 2012), and so the rate of decline may be lower than previously thought. If there is sufficient evidence to suggest that the rate of decline is not more than 30% over three generations, this species would no longer qualify as Vulnerable under the A criterion and would warrant downlisting to Near Threatened. Nevertheless, little is known about the nesting success of the Lesser Adjutant and in long-lived species such as this, populations can remain stable for long periods even when breeding has ceased to be a profitable activity (S. Mahood in litt. 2012).
Information is requested on this species’s population trends, population size and breeding success. Any further comments on the proposed downlisting are welcome.
Bird, J. P., Mulligan, B. and Gilroy, J. (2007) Cambodia ornithological expedition 2006.
Li, Z.W.D., Yeap, C. A. and Kumar, K. (2007). Surveys of coastal waterbirds and wetlands in Malaysia, 2004-2006. In: Li, Z. W. D. and Ounsted, R. (ed.), The status of coastal waterbirds and wetlands in Southeast Asia: results of waterbird surveys in Malaysia (2004-2006) and Thailand and Myanmar (2006), pp. 1-40. Wetlands Internationa: Kuala Lumpur.
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