Philippine Hawk-owl (Ninox philippensis) is being split: list N. leventisi and N. rumseyi as Endangered, N. reyi and N. mindorensis as Vulnerable, and N. spilonota and N. philippensis as Near Threatened?

This is part of a consultation on the Red List implications of extensive changes to BirdLife’s taxonomy for non-passerines

Lynx Edicions and BirdLife International will soon publish the HBW-BirdLife Illustrated Checklist of the Birds of the World, building off the Handbook of the Birds of the World series, and BirdLife’s annually updated taxonomic checklist.

The new Checklist will be based on the application of criteria for recognising species limits described by Tobias et al. (2010). Full details of the specific scores and the basis of these for each new taxonomic revision will be provided in the Checklist.

Following publication, an open and transparent mechanism will be established to allow people to comment on the taxonomic revisions or suggest new ones, and provide new information of relevance in order to inform regular updates. We are also actively seeking input via a discussion topic here regarding some potential taxonomic revisions that currently lack sufficient information.

The new Checklist will form the taxonomic basis of BirdLife’s assessments of the status of the world’s birds for the IUCN Red List. The taxonomic changes that will appear in volume 1 of the checklist (for non-passerines) will begin to be incorporated into the 2013 Red List update, with the remainder, and those for passerines (which will appear in volume 2 of the checklist), to be incorporated into subsequent Red List updates.

Preliminary Red List assessments have been carried out for the newly split or lumped taxa. We are now requesting comments and feedback on these preliminary assessments.

Philippine Hawk-owl Ninox philippensis is being split into N. philippensis, N. mindorensis, N. spilonota, N. spilocephala, N. rumseyi, N. leventisi and N. reyi.

Prior to this taxonomic change, N. philippensis (BirdLife species factsheet) was listed as Least Concern, as it was estimated to have a very large range, and hence was not thought to approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence [EOO] 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). The population trend appeared to be stable, and hence the species did not approach the thresholds for Vulnerable under the population trend criterion (at least a 30% decline over ten years or three generations). The population size has not been quantified, but it was not believed to 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).

N. rumseyi is found on Cebu, where it inhabits remnant forest fragments (Rasmussen et al. 2012). This newly defined species may qualify as Endangered under criteria B1ab(ii,iii,v); C2a(ii), on the basis that it has a very small range (with an EOO estimated at c.4,400 km²),in which suitable habitat is severely fragmented and in decline, with a continuous decline inferred in the population, which is estimated to be very small (c.400 mature individuals; Jakosalem et al. in press per Rasmussen et al. 2012) and probably forms a single subpopulation.

N. leventisi is found on Camiguin Sur (Rasmussen et al. 2012). It may qualify as Endangered under criterion C2a(ii), on the basis that it is estimated to have a very small population (fewer than 2,500 mature individuals), which likely forms a single subpopulation and is inferred to be in decline owing to on-going habitat loss and fragmentation.

N. reyi is found on Sulu, Siasi, Tawi-Tawi, Sanga Sanga, Bongao and Sibutu (Rasmussen et al. 2012). It may qualify as Vulnerable under criterion C2a(i), on the basis that, although it probably has a very small population (fewer than 2,500 mature individuals), and the overall population is inferred to be in decline owing to on-going habitat loss and fragmentation, some subpopulations probably number more than 250 mature individuals (thus the subcriteria are not met for listing as Endangered).

N. mindorensis is found on Mindoro (Rasmussen et al. 2012). It may qualify as Vulnerable under criterion B1ab(ii,iii,v), on the basis that it has a small range (with an EOO estimated at c.9,900 km²), in which suitable habitat is severely fragmented and being lost and degraded owing primarily to clearance for agriculture, with a decline inferred in the population as a result.

N. spilonota is found on Sibuyan and Tablas (Rasmussen et al. 2012). It is suggested that it be listed as Near Threatened under criteria B1ab(iii,v); C2a(i), on the basis that, although it has a very small range (with an EOO estimated at c.1,100 km²), in which the area and quality of habitat are in decline, it is not yet severely fragmented; the species’s population is thought to be small (fewer than 10,000 mature individuals) and is inferred to be in decline, but there are probably more than 1,000 mature individuals in each subpopulation (thus the subcriteria for listing as Vulnerable are not met).

N. spilocephala is found on Mindanao. It is suggested that it be listed as Near Threatened under criteria A2c+3c+4c, on the basis that it could be undergoing a moderately rapid population decline (approaching 30% over three generations [c.12 years]) owing to on-going habitat loss and degradation.

N. philippensis (as defined following the taxonomic change) is found on Biliran, Bohol, Boracay, Buad, Carabao, Catanduanes, Guimaras, Leyte, Lubang, Luzon, Marinduque, Masbate, Negros, Panay, Polillo Samar, Semirara, Siquijor and Ticao (Rasmussen et al. 2012). It is suggested that it be listed as Near Threatened under criteria A2c+3c+4c, on the basis that it could be undergoing a moderately rapid population decline (approaching 30% over three generations [c.12 years]) owing to on-going habitat destruction throughout its range.

Comments are invited on these suggested categories and further information would be welcomed.

References:

Rasmussen, P. C., Allen, D. N. S., Collar, N. J., DeMeulemeester, B., Hutchinson, R. O., Jakosalem, P. G., Kennedy, R. S., Lambert, F. R. and Paguntalan, L. M. (2012) Vocal divergence and new species in the Philippine Hawk Owl Ninox philippensis complex. Forktail 28: 1-20.

Tobias, J. A., Seddon, N., Spottiswoode, C. N., Pilgrim, J. D., Fishpool, L. D. C. and Collar, N. J. (2010) Quantitative criteria for species delimitation. Ibis 152: 724–746.

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