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 [1],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.