Archived 2010-2011 topics: Tablas Drongo (Dicrurus menagei): list as Endangered?

Tablas Drongo Dicrurus menagei has been split from Hair-crested Drongo D. hottentottus following del Hoyo et al. (2009). D. menagei is found only on Tablas Island in west-central Philippines, where by 1997 it was considered probably extinct after many decades without any reports. Observations since 1998, however, have confirmed that the species is extant, albeit rare (Allen 2006).

It is found in relatively mature, closed-canopy forest, with occasional records from the edge of clearings, but it is absent from open areas (Allen 2006). Evidence suggests that the species’s habitat is in decline. Extensive forest clearance is believed to have taken place on Tablas Island since the beginning of the 20th Century, with a substantial proportion of the island now used for cultivation and livestock-rearing. Rice fields are common in lowland areas, while rough pasture and coconut plantations are found in the hills. Remnants of original forest over 10 m tall are present only around the summit and south-eastern slopes of Mt Palaupau, where forest is maintained as a watershed for nearby settlements. There are reportedly very few registered forest patches that exceed 100 ha, and apparently a complete lack of mature forest in the south of the island (Allen 2006; del Hoyo et al. 2009). This suggests a high degree of habitat fragmentation; however, to be considered severely fragmented over 50% of the species’s habitat must be in patches too small to support viable populations. Small-scale logging is still a threat (del Hoyo et al. 2009), suggesting that habitat is still being lost.

Although data are lacking on its population size and exact distribution, it is proposed that this species be listed as Endangered under criterion B1a+b(i,ii,iii,iv,v), on the basis that it occupies an Extent of Occurrence (EOO) liberally estimated at 680 km2 (approximate total area of Tablas Island), in which its habitat is provisionally considered to be severely fragmented, and ongoing declines are suspected in the EOO, Area of Occupancy, area, extent and quality of habitat, number of locations or sub-populations and number of mature individuals. These declines are suspected because of ongoing habitat loss and degradation.

Comments are invited on this proposed listing and additional information is requested to assist in the evaluation of the species’s threat status.

Allen, D. (2006) New records and other observations of birds on the island of Tablas, Philippines. Forktail (22): 77-84.

del Hoyo, J., Elliott, A. and Christie, D. A. eds. (2009) Handbook of the Birds of the World, vol. 14: Bush-shrikes to Old World Sparrows. Barcelona, Spain: Lynx Edicions.

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3 Responses to Archived 2010-2011 topics: Tablas Drongo (Dicrurus menagei): list as Endangered?

  1. I am glad that our suggestion to split Tablas Drongo from Hair crested Drongo has been followed; and I fully support its proposed listing as Endangered based on the text written by D. Yeatman-Berthelot and myself in the HBW

  2. Joe Taylor says:

    The following comments were received from Edward Dickinson on 19 January 2011:

    Thank you for the invitation. However, I am really no longer sufficiently up-to-date on Philippine birds.

    I guess my contribution on Dicrurus [hottentottus] menagei comes in two halves:

    a) It is certainly morphologically very distinctive and the idea of treating it as a species is attractive — just because of how distinctive it is.

    b) molecular studies on drongos probably have a long way to go; certainly all the forms associated with D. hottentottus sensu lato have not been sampled, and equally I am not convinced we yet understand the colonization history — except to feel increasingly clear that drongos reached the Philippines in three or more invasions over time — with a probability that some stepping stone islands which were once subaerial are now long drowned, and, thirdly, I wonder if enough of the genome has been sampled? Also consider the gene tree versus species tree debate!

    On balance while a year ago I would have voted for assigning species status to this, I am less comfortable about that to-day because of developments in our understanding of what is important in molecular sampling and analysis, and in the drawing of sound conclusions; generally speaking there are/have been a few too many rushes to judgement based on unacceptable gaps in sampling of species represented. While it is evident that many things need to be unlumped (especially in the Philippines, which “enjoys” an unusually conservative historical judgement process), premature unlumping will very likely just confuse everyone if we have to back-pedal in a few years.

  3. Joe Taylor says:

    The following comments were received from Desmond Allen on 27 January 2011:

    I am not sure about the present state of the forest but i doubt it has contracted much since I wrote for Forktail (quoted in HBW etc). However the population must be very small, and it must at least be Endangered, possibly Critical. It doesnt occur at high density even within the remaining forest and there may be fewer than 50 pairs.

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