Archived 2011-2012 topics: Knobbed Hornbill (Aceros cassidix) and Sulawesi Hornbill (Penelopides exarhatus): uplist to Near Threatened?

This discussion was first published as part of the 2007 Red List update.

Initial deadline for comments: 31 January 2012.

Knobbed Hornbill Aceros cassidix and Sulawesi Hornbill Penelopides exarhatus are both currently listed as Least Concern.

However, a recent reanalysis by Kinnaird and O’Brien (2007) has suggested that both species are declining at rates approaching 30% over ten years/ three generations based on recent and ongoing rates of habitat loss on Sulawesi [16.9% forest loss per ten years during 1985-1997; 36.1% loss per ten years during 1997-2001 based on D. A. Holmes in litt. 1999 and Kinnaird and O’Brien (2007)]. This would qualify them for Near Threatened (almost meeting criteria A2c;A3c). Sulawesi Hornbill may also approach the thresholds under criterion C2b (population approaching 10,000 mature individuals, declining with extreme fluctuations), as MacKinnon and MacKinnon (1980) documented a dramatic crash in the population at Tangkoko in 1978-1979. T. O’Brien and M. Kinnaird (in litt. 2006) have speculated that this may be driven by disease introduced by domestic poultry into wild populations. Does it seem likely that this species undergoes order-of-magnitude population size fluctuations?

Comment and information relevant to the proposal to uplist these species would be welcome.

Kinnaird, M.F. and O’Brien, T.G. 2007. Ecology and Conservation of Asian Hornbills. Univ. Chicago Press

(This discussion was first started as part of the 2007 Red List update)

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2 Responses to Archived 2011-2012 topics: Knobbed Hornbill (Aceros cassidix) and Sulawesi Hornbill (Penelopides exarhatus): uplist to Near Threatened?

  1. Andy Symes says:

    Regarding population fluctuations in Sulawesi Hornbill, Tim O’Brien has added (June 2007):
    “MacKinnon and MacKinnon described a crash in the tarictic population in 1978 management plan for Tangkoko Nature Reserve. Our census in 1992-93 indicated that the population had recovered. We discuss this in our paper in tropical biodiversity O’Brien, T.G. and M.F. Kinnaird. 1994. Notes on the density and distribution of the endemic Sulawesi tarictic hornbill (Penelopides exarhatus exarhatus) in the Tangkoko-Dua Saudara Nature Reserve, North Sulawesi. Tropical Biodiversity 2:252-260.”

    operations (January 2009):
    Recent work by BirdLife International (unpublished data) has calculated generation lengths of 19.0 years for Knobbed Hornbill and 19.4 years for Sulawesi Hornbill; hence population trends should be calculated over a timeframe of 57 and 58 years respectively. Given that the global population of Sulawesi Hornbill had recovered by the mid 1980s following a crash in the late 1970s we cannot extrapolate declines back beyond that time, but if current rates of forest loss continue these species will easily approach the thresholds for listing under a threatened category on the Red List. Near Threatened would seem to be a conservative assessment. To uplist further may require evidence of rates of forest loss within these species’s ranges.

    Dwi Mulyawati (February 2010):
    Since founded, Burung Indonesia never work in Sulawesi mainland but starting on 2009, Burung Indonesia establishes a new restoration ecosystem, this new approach of conservation initiative within Indonesia forest will be benefit to human and also the birds inhabited the forest.

    Based on our field study on Gorontalo, Sulawesi, on primary and abandoned selectively logged forest, both Hornbills are relatively easy to encounter while some part of the forest is nearby human settlement. Gorontalo lowland forest is just small part of both species range, meanwhile the Knobbed Hornbill is the only large frugivores which has high encounter rate (Burung Indonesia unpublished data), and up to 12 birds seen in one occasion during the midday and a pair also seen using single tall trees adjacent to human habitation to forage.

    • Frank Lambert says:

      Adult hornbills can probably survive long after their breeding potential has been destroyed, so their presence does not necessarily indicate very much. Long-lived birds like hornbills that have highly specialised breeding requirements (such as holes in big trees) may be much more threatened than the impression given by their apparent abundance.

      It is also worth noting that a taxonomic study of Penelopides in Sulawesi might show that sandfordi and exarhatus are good species.

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