Since 1945, Philippine Hawk-owl has been treated as a single species, Ninox philippensis, with eight subspecies. Now a paper in the Oriental Bird Club journal, Forktail ,co-authored by a BirdLife scientist, proposes that the hawk-owls of the Philippines form a complex of seven species from different islands and island groups, including two that have not previously been described at any taxonomic level. These two undescribed species have been given scientific names honouring two conservationists and long-term supporters of BirdLife International.
These owls group into three distinctive plumage types: one with all-streaked underparts and plain crowns, one with mottled or barred breasts, streaked lower underparts, and spotted crowns, and one with barred to nearly plain underparts (the ‘unstreaked’ group).
Although specimens have been in museum collections for many years, sound recordings were until recently available only for a few island forms, and most were incomplete and of poor quality.
These recordings were, however, adequate to establish that the Mindoro form mindorensis differs profoundly in vocalisations (thin high-pitched whistles and hoarse rasps) from the nominate Luzon form philippensis (a series of mid-pitched barking notes), prompting the separation of Mindoro Hawk-owl N. mindorensis in 1999.
New fieldwork targeting morphologically distinctive Ninox taxa has provided nearly complete sampling of the vocal repertoires of key island populations, and thereby made it possible to resolve the species limits in the Philippine Hawk-owl complex. (The recordings can be accessed at http://avocet.zoology.msu.edu/recordings/14561)
The recordings reveal an extraordinary degree of differentiation in a group of birds for which vocal communication is of paramount importance in species recognition.
“Hawk-owls that differ in plumage also differ in vocalisations, so much so that their treatment as one species in a group with innate vocalisations such as owls is untenable”, said Dr Nigel Collar, co-author of the paper, and Leventis Fellow in Conservation Biology at BirdLife International.
On the basis of their analysis, the authors propose the following arrangement for the N. philippensis complex:
Luzon Hawk-owl Ninox philippensis
Mindanao Hawk-owl Ninox spilocephala
Mindoro Hawk-owl Ninox mindorensis
Romblon Hawk-owl Ninox spilonota
Cebu Hawk-owl Ninox rumseyi
Camiguin Hawk-owl Ninox leventisi
Sulu Hawk-owl Ninox reyi
The previously undescribed Camiguin Hawk-owl was named for Anastasios P. Leventis, BirdLife Vice President, BirdLife Patron, former BirdLife Treasurer and long standing supporter of BirdLife International. He has been crucial in the stable development of the organisation, and particular support for Nigel Collar has allowed Collar to work extensively on Philippine birds and conservation issues over the past decade. Cebu Hawk-owl was named for the conservationist and ornithologist Stephen J. Rumsey, also a BirdLife Patron, former BirdLife Treasurer and long term supporter who has helped promote research and conservation on the island of Cebu.
The conservation status of these various forms awaits full evaluation. BirdLife International, as the Red List Authority for the world’s birds on behalf of the IUCN, will evaluate the new species’ Red List category in the 2013 Red List update. However, five species -from Mindoro, Romblon, Cebu, Camiguin and Sulu- are likely to be at risk.