BirdLife species factsheet for Lesser Adjutant
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.
References:
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.
Related posts:
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- Lesser Masked-owl (Tyto sororcula): reassess as Vulnerable?
- Archived 2011-2012 topics: Lesser Florican (Sypheotides indicus): request for information
- Archived 2011-2012 topics: Greater Scaup (Aythya marila): uplist to Near Threatened or Vulnerable?
- Archived 2011-2012 topics: White-necklaced Partridge (Arborophila gingica): downlist to Near Threatened?
Lesser adjutant is the most frequently recorded large waterbird in the decidious dipterocarp forests of eastern Cambodia.
However given the pervasive and accelerating threats to this habitat from unregulated economic and social land concessions I believe it is sensibly precautionary to predict minimum future 30% decline (at least in Cambodia) in next three generations. Given the species’ scarcity in the degraded DDF of southern Laos, Vietnam, Thailand together with the uncertainity for the species’ prospects in Cambodia down-listing would, in my opinion, not be sensible.
As S. Mahood said in 2012 “In addition, calculating the rate of decline for a widespread species which occurs in relatively low numbers is difficult…” so just as you tagged on that the rate might be lower than previously thought, it might also be higher, or the same.
Lesser Adjutant has benefited from conservation action in Cambodia, both as a result of nest protection in the deciduous dipterocarp forest and colony protection at Prek Toal. In the latter the population is growing and currently numbers some 350 pairs (this represents c. 10% of the Cambodian population). However, overall the population is still declining at a rate equal to or above the rate of forest degradation (important because degradation = people in the forest = hunting) and loss.
Habitat conversion continues at an incredible pace in Cambodia, and, since this country supports most of the global population it would be wise to assume that the current and future rate of decline exceeds 30% over three generations. I do not support downlisting.
Current status and distribution of the Lesser Adjutant in Bangladesh is summarized here: Chowdhury, S.U. & Sourav, S.H.M. 2012.Discovery of a Lesser Adjutant Leptoptilos javanicus breeding colony in Bangladesh. BirdingAsia 17: 56.
The following comments were received from Muhammad Iqbal on 4 April 2013:
Sumatra is one important habitat for this species. I am afraid that this bird decline in Sumatra caused by loss breeding areas; convertion mangrove forest as fish pond and peatswamp forest as Acacia plantation. I will check the number in the future to make comparison.
With a 48-year window for assessment, and looking at the battery of threats facing lowland areas well supplied with wetlands, from sea-level rise (not just direct loss of adjutant areas, but displacement of people through loss of farmland to look for new areas) to plantation agriculture, a proposal to change from VU to NT would have to be very well justified. I don’t see any evidence above that it is, particularly not for likely future population trends. Moreover, few people nowadays probably have any perception of how common this species may well have been 50 years ago (i.e. start of window for past decline to meet 30% or more) – anyone who has seen the Wharton Kouprey film cannot fail to have been taken aback at the large number of large waterbirds in the background scenery. The perception that there are actually rather more now than any one thought, and that in one area declines have been reversed, needs to be seen in a time window far longer than with most SE Asian birds. I think this is a good example of the phenomenon labelled in an issue of Oryx a few years ago as “less and less-great expectations’, because there are no people around able to tell us just how badly this species is doing over the last 3 generations. The fact that its rate of decline in the last 20 years (a typical average assessment period for birds) probably does not approach VU may be instilling a misleading sense of security here. The Tonle Sap colony success needs to be replicated a good deal more widely if the global population trend is to be materially affected. Besides, who feels they can safely predict whether the Great Lake of Tonle Sap will even exist in 2060, given current serious proposals for Mekong catchment megadams and the Great Lake’s dependence on high enough wet-season Mekong levels to reverse the (river) Tonle Sap flow and refill the Great Lake every year. If asked which direction the category should go from VU I’d say EN more likely than NT!