The Sulawesi Masked Owl
was the first of the endemic Tyto
owls I saw. It is found more or less throughout the island (this photo from
central Sulawesi) and on some smaller islands (I will do a separate post of one
of the island subspecies that I found interesting). This is a large and dark Tyto owl (can reach 51 cm) with powerful
talons. You can see in this photo that the hints of gold in the plumage are
rather limited and the central crown is grey despite a golden wash on the neck
sides. Very little is known about this species, even basic information on its diet
and nesting is rather lacking. Like so many Tyto
species, the Sulawesi Masked Owl has some affinity with caves and one of
the few known nesting records was in a sea cave near Tangkoko (others in tree cavities). This species occupies
a wide variety of habitat types, from forests to rural areas and even grassland
interspersed with trees but is less of a true forest owl than the Minahassa
Masked Owl (below). The individual in the photo below was seen in rather open wooded
area near the village of Sedoa in central Sulawesi at approximately 1250 m ASL.
The pelengensis race of the Sulawesi Masked
Owl, from the islands of Banggai and Peleng, is very poorly known and seldom
seen. It was an extraordinary privilege to see one by night and one by day with
the help of Alpian Maleso. It appears MUCH
smaller than the nominate race of Sulawesi Masked Owl, which took me so much by
surprise that I thought I was looking at a Minahassa Masked Owl for a second
(but a few features such as the less dense feathering on the lower tarsi tipped
me off, not to mention the fact that Minahassa Masked Owl is not supposed to
occur on these islands). Given that there is an endemic Tyto on the island of Taliabu, the Taliabu Masked Owl (which was the
one owl species on that trip that I saw but did not manage to photograph), and
that there are some commonalities between Peleng/Banggai and Taliabu (Sula
Islands), this taxon deserves more detailed
study.
Sulawesi
Masked-Owl (Tyto rosenbergii pelengensis), Peleng
Island, Indonesia, © Christian Artuso.
Rare, poorly known, a
deep forest (rainforest) species that is range restricted, bring confined to
the northern peninsula of Sulawesi, known as the Minahas Peninsula, plus a
small portion of the central region around Lore Lindu National Park, the
Minahassa Masked Owl is listed as globally Vulnerable
to extinction. It is similar in appearance to the Sulawesi Masked Owl but
much smaller in size with a rounder and smaller facial disk with a pink wash,
as well as a golden colour in the central crown (compare the previous photos of
Sulawesi Masked Owl with its grey central crown despite gold on the neck sides).
This enigmatic owl is highly sought after by naturalists who visit Sulawesi,
though rarely seen. Once in a while, the numerous guides at Tangkoko know of a
roost site and lucky observers get to see it that way. For myself, and most
visitors, however, this typically proves one of the toughest of the Sulawesi
endemics to see. Fool that I be, I was visiting in the rainy season and no
roost of any owls were reliable (not even the common species). After three nights
alone in the Tangkoko forest, with not so much as a peep, I finally heard a
Minahssa Masked Owl near 4 am on my third night. The unmistakable, incredibly loud hiss came after
I had been hiding out from the rain in a fallen, hollow tree and managed to get
bites all over my legs from some unknown chigger-like creature. What followed
was an intense 30 minutes of me trying to tip-toe through the rainforest,
without using my headlight, towards the sound until the beast called a second
time. At that point, I miraculously managed to find it perched in the subcanopy
for a couple of precious minutes. The small size and heavily feathered, golden
legs were obvious right away and, when that round, pinkish face, with golden
crown, turned into view, all that discomfort and sleep deprivation were soon
forgotten! Along with the Taliabu Masked Owl, this was the trip’s biggest
highlight.
Minahassa
Masked-Owl (Tyto inexspectata), northern Sulawesi,
Indonesia, © Christian Artuso (Note: I have used IOC spelling but the region
name and the species name are spelled “Minahasa” by Birdlife International and
others).
Since I did not manage to
photograph the Taliabu Masked Owl, the only remaining Tyto to post about is the Eastern Grass-Owl, also known as the
Australasian Grass-Owl. This species found from Australia, through New Guinea,
Sulawesi, the Philippines and other islands, all the way to parts of China and
India, though absent in many intervening areas. The name Australasian Grass Owl
may seem odd; however, this owl seems more common in the Australasian parts of
its range and I have always struggled to see it in Asia. This large and
long-legged Tyto is a denizen of
grasslands, vegetated wetlands, and other areas with tall grass or grass-like
vegetation (this can include some cropland such as cane fields). I thoroughly
enjoyed watching this owl sail over the rice paddies of the Napu Valley in
central Sulawesi at dusk. You can see how the toes project well beyond the tail,
the long legs presumably a useful adaptation for a predominantly
ground-dwelling species in grassy habitats. In that sense, the grass owls (Eastern
Grass Owl and African Grass Owl) have something in common with the Burrowing
Owl of the Americas, though they are much larger. This Eastern Grass Owl was too far away and
the light too dim for good photos but, nonetheless, this was an especially
sweet experience as I had not managed a photo of this species when I saw it in
the Philippines.
Eastern Grass Owl
(Tyto longimembris), central
Sulawesi, Indonesia, © Christian Artuso.
From the barn
owl family (Tytonida), we move to the typical owl family (Strigidae). The Otus
owls are very common in Asia but as one moves east into the Australasian realm
they decrease in diversity. There is typically only one species (often endemic)
on the islands of “Wallacea” / eastern Indonesia. There are no Otus owls that
regularly occur on mainland Australia or the main island of New Guinea,
although one species is endemic to a small island off western New Guinea called
Biak. Sulawesi has its endemic Otus owl, not surprisingly called Sulawesi Scops
Owl. Some of Sulawesi's satellite islands and the islands east of Sulawesi (the
Moluccan Islands or Maluku) are also home to an Otus species. It is only
fitting I start with the Sulawesi Scops Owl, which comes in two colour morphs
(brown and rufous), this being a brown morph from the Tangkoko area. This
species is quite common throughout the island of Sulawesi from sea level to at
least 2500 m ASL.
Sulawesi
Scops-Owl (Otus manadensis), northern
Sulawesi, Indonesia, © Christian Artuso.
Although considered a full species
by some taxonomists, the Banggai Scops Owl is listed as a subspecies of Sulawesi
scops by the IOC. It is nonetheless smaller with a different call and other
differences. It is IUCN red-listed as Vulnerable to extinction because the
population is thought to be very small. If you accept it as a species then it
is confined to one or two islands, Peleng Island and probably also Banggai Island. Peleng has suffered considerable habitat loss, which is part of the
concern for this species.
Banggai Scops-Owl
(Otus [manadensis] mendeni), Peleng
Island, Indonesia, © Christian Artuso.
The small island of Sangir
Besar (largest island in the Sangihe Island group) is less than 600 km2
square and roughly half way between Sulawesi and the Philippines. It is home to
some unique (endemic) species including this scops owl, many of which are
highly endangered. There are many small island endemic Otus species, so the fact that one lives solely on this tiny island is not surprising. The Sangihe Scops Owl is also known by the
name Sangir Scops, which is technically a better name since there is, or at
least was, another Otus species in
the Sangihe group on the island of Siau (possibly extinct). As the Sangihe Scops Owl seems able to use a variety
of habitats including secondary growth and human-altered habitats, it is not on
the brink of extinction like some of the other Sangir endemics.
Sangihe Scops-Owl
(Otus collari), Sangihe
Island, Indonesia, © Christian Artuso.
The Sula Scops Owl is a
little bit of a mystery. It is treated in some taxonomies as a subspecies of
Sulawesi Scops Owl but it is strikingly different to that species in voice and
morphology (several authors have suggested that it is probably most closely
related to the Moluccan Scops Owl). Many taxonomies, including the IOC, now
give it full species status. As the name suggests, it is endemic to the island
group called the Sula Islands, being found on Taliabu, Seho, Mangole, and possibly
also on Sulabes (my sources conflict on whether it occurs on Sulabes or not). The Sula Scops Owl is smaller than the Sulawesi
Scops Owl with a deeper colour, smaller ear-tufts and other differences,
especially the calls. This photo was taken near the village of Binadessa on the
island of Taliabu.
Sula Scops-Owl (Otus sulaensis), Taliabu Island,
Indonesia, © Christian Artuso.
In addition to the Otus scops owls, the other important
genus of owls on Sulawesi and its neighbouring small islands is Ninox. The owls of the genus Ninox are often called “boobooks”, an onomatopoeiac word describing the
two-syllable call of the Southern Boobook, although many members of this genus
have similar disyllabic calls. The Ninox
genus owls also get referred to as “hawk owls” (in names as the Brown Hawk Owl Ninox scutulata), although they are not
closely related to the Northern Hawk Owl (genus Surnia). Some Ninox owls
do have a bit of a hawk-like appearance; especially the large ones with a weak
facial disk (see my earlier posts on the Powerful Owl and the Barking Owl). The
genus Ninox has a mostly Australasian
and Southern Hemisphere distribution (a few reach Asia and the Northern
Hemisphere) and is the only genus of typical owls (Strigidae) that occurs
regularly in Australia. There are three Ninox
species on Sulawesi (some would say possibly a fourth, which I will discuss
later) and one on a satellite island.
The Ochre-bellied
Boobook is a Sulawesi endemic but it has a somewhat patchy distribution on the
strangely shaped island. There are sightings on some of the small islands as
well. It seems to prefer dense, moist forest types and because of its
restricted range, seemingly small population, and somewhat narrow habitat
requirements (making it vulnerable to logging), it is considered “Near
Threatened”.
Ochre-bellied
Boobook (Ninox ochracea), northern
Sulawesi, Indonesia, © Christian Artuso.
The Cinnabar Boobook is even more
range restricted than the Ochre-bellied Boobook, occurring only above 1,000 m
ASL and in isolated mountains on the northern peninsula (Minahas Peninsula) and
then, maybe, in isolated mountains of central and southern Sulawesi. I say
“maybe” because the undescribed taxon in central and southern Sulawesi has some
mystery surrounding it, i.e. it remains unclear if it is a subspecies of
Cinnabar Boobook or, some have argued, perhaps a separate species. I will post
three photos northern Cinnabar Boobook below (from Gunong Ambang) and then one from
central Sulawesi (Lore Lindu). The first photo shows a pair of Cinnabar Boobooks on
a day roost (a very lucky find) and then two night photos are added (one showing the underparts). The
most interesting thing about the four owls I saw at Gunong Ambang (two by day,
two by night) was the very obvious white spots or scalloping on the underparts
(when seen by day and by night). Most photos of the northern birds show limited
white spotting on the underparts, certainly much less white spotting than this!
In fact, the presence of white spots on the underparts is said to be one of the
differences of the central Sulawesi birds, but my experience contradicted this.
Due to its very restricted range and apparent rarity (it was only described to
science in 1999), the Cinnabar Boobook is listed as globally Vulnerable to
extinction.
Cinnabar Boobook (Ninox ios), northern Sulawesi,
Indonesia, © Christian Artuso.
The undescribed Ninox owl of the highlands of central Sulawesi that looks and
sounds very much like the Cinnabar Boobook is referred to as the “White-spotted
Boobook” because the underparts are supposed to have more white than the
northern peninsula birds. For this reason, I was especially keen to see this
owl at Lore Lindu and when I did I was pleased to note the white-scalloped
underparts as shown in this photo. I heard and saw this owl before I went to
northern Sulawesi and thought little of it. When I went to Gunong Ambang and
heard the Cinnabar Boobook there, it sounded identical to my ears to the owls
at Lore Lindu, both a gruff, soft tok-tok
that seemed soft but was probably far
carrying. Others have said that the call of these two is not quite the same but
I could not discern any differences (maybe it needs a spectrogram). After I
heard the Cinnabar Boobook at Gunong Ambang, I managed to see it. I was
surprised that the boobooks here had more extensive white spotting than this
bird from Lore Lindu. I don’t really have a good explanation for this other
than individual variation. I was visiting Sulawesi in the rainy season when
very few birders go, but a seasonal plumage change seems highly unlikely.
Perhaps I saw aberrant individuals in both case but, if so, there was more than
one of each. I did some online searching and found photos that show a range of
plumage in northern Cinnabar Boobooks from almost unspotted to rather “scalloped”. This makes me think these owls are rather
variable. I have read that the white-spotted form also has a more prominent
white supercilium than the northern form but that did not seem to be the case
(perhaps because they were so high in the canopy at Lore Lindu that I was
unable to see the supercilium properly). Comments certainly welcome from those
with more experience with these taxa….
“white-spotted” Cinnabar
Boobook (Ninox ios), central Sulawesi, Indonesia,
© Christian Artuso
The Speckled Boobook is
an intriguing species, not least because of its hilarious, slow-building, maniacal call
that is so different from the disyllabic call of most Ninox owls. Have a listen at https://www.xeno-canto.org/species/Ninox-punctulata
for a good chuckle! Speckled Boobook also seems to be the Ninox species with truly dark eyes.
There is some variation in the eye colour of Speckled Boobooks, from dark brown
to a lighter brown and some texts like Handbook of Birds of the World say even
to orange-yellow (but none of the photos I have found show orange-yellow eyes).
The White-browed Owl of Madagascar has dark eyes and used to be placed in the
genus Ninox, but is now considered an
Athene. Brown eyes do also occur in
some other species such as the Moluccan Boobook, but this may be age dependent, and the
Russet Boobook has orange-brown eyes. Some
subspecies of widespread Ninox
species may show variation in eye colour, e.g., some subspecies of Southern
Boobook have somewhat brownish eyes, though most are yellow. In short, the
Speckled Boobook may not be completely unique in this aspect but it is unusual.
This is a widespread Sulawesi endemic, found on most of the island except high
elevations. It seems to be able to utilise rather open forests and
human-altered habitats more than the other endemic Ninox species of Sulawesi that I posted about previously and is
not considered threatened.
Speckled Boobook (Ninox punctulata), central Sulawesi,
Indonesia, © Christian Artuso.
The Togian Islands in the Gulf of
Tomini (created by Sulawesi’s strange “armed” shape) have a few endemics of
their own, despite their proximity to the main island. One of these is the
Togian Boobook, a beautiful Ninox owl
found on at least three islands in this group (Malenge, Togian and Batudaka),
that was first described to science in 2004. The ferry schedule permitted me
only one night on Batukada so I had to make the most of it. Fortunately for me,
several of these owls were calling that night and they seemed to be in both the
forested area and farmland edge. I still consider myself lucky to have spotted
this individual at dusk. This species is considered Near-threatened, mostly
because of its tiny global range and concern over ongoing deforestation in the
islands (even if Batukada and Togian were made into a national park in 2004,
there still seems to be a lot of clearing going on).
Togian Boobook (Ninox burhani), Batukada Island,
Indonesia, © Christian Artuso.
An unexpected bonus on
my night hike on Batukada
Island was spotting this perched Northern Boobook at the forest edge out of the
corner of my eye. This bird was not calling, which is not surprising because this
species is a winter visitor to this part of Indonesia, breeding in eastern Asia
(eastern Russia, China, the Korean peninsula and Japan). As such, it is the
northernmost member of its genus! The Northern Boobook was only recently split
from the extremely similar Brown Hawk Owl (or Brown Boobook). It is perhaps the
only Ninox owl with a true migration,
although the Tasmanian Boobook may also migrate north to mainland Australia (it is still not clear if this is a dispersal or a true migration).
Northern Boobook (Ninox japonica), Batukada
Island, Indonesia, © Christian Artuso.
I
hope you enjoyed this introduction to the owls of Sulawesi!
