On a recent trip to
Costa Rica I saw 13 species of owl. This blog pot discusses those species that
I managed to get good photos of, which is most of the country’s owls.
Bare-shanked
Screech- Owl (Megascops clarkii), reddish-brown morph
The Bare-shanked Screech-Owl is endemic to
the mountains of Costa Rica, Panama and extreme northwestern Colombia (from
approx.. 900m – 3200m ASL but usually more common in the mid elevation cloud
forest and humid forest). The first photo shows the bare shanks that gives the
species its name. The second photo shows the wing droop display posture when
delivering the territorial song. This is a red morph individual, which seemed
more common in the parts of Costa Rica I visited than the dark brown morph.
Pacific
Screech-Owl (Megascops cooperi)
The Pacific Screech-Owl occurs in a
relatively narrow strip along the Pacific coast from southwestern Mexico
(Oaxaca and Chiapas) to northwestern Costa Rica (mostly Guanacaste). This is a
resident of dry forest types (also mangroves in some contexts), mostly in the
lowlands but sometimes as high as 1000m ASL, although this individual
photographed by Adrian Arroyo and myself in Monteverde, Costa Rica is at
roughly 1300m ASL. Although common in its limited range, this is a poorly known
species. This is one of the few species of Megascops
that is not known to have a red morph (this follows the general pattern of
higher prevalence of red morph birds in humid environments).
Vermiculated
Screech-Owl
complex in Costa Rica
Four photos
showing:
* (Megascops vermiculatus), brown morph,
Monteverde, Costa Rica,
* (Megascops guatemalae or vermiculatus), reddish-brown morph, Boca
Tapada, Costa Rica.
It is worth stating
firstly that there is little agreement on the species status of the various
taxa within the Vermiculated Screech-Owl complex. Though some only recognise
one or two species, others such as the IOC treat this group as five distinct
species as follows:
* Middle American
Screech-Owl (Megascops guatemalae)
* Vermiculated
Screech-Owl (Megascops vermiculatus)
* Roraiman
Screech-Owl (Megascops roraimae)
* Napo Screech-Owl
(Megascops napensis)
* Choco Screech-Owl
(Megascops centralis)
With the help of
Adrian Mendez and Adrian Arroyo, I photographed this brown individual (first
two photos) in Monteverde on the Pacific slope at approximately 1300 m ASL. I
photographed this reddish-brown individual (third and fourth photos) near Boca
Tapada in the Caribbean lowlands in the extreme north of the country. The issue
for me was that the bird in Monteverde gave what I consider to be a typical
song for M. vermiculatus, i.e. a very
rapid trill that lasted approx. 8 seconds, whereas the bird I heard in Boca
Tapada gave a very long trill that I timed at 20 seconds in duration and which
struck me as more akin to M. guatemalae.
Based on song along, I was inclined to think that two different species are
present in Costa Rica (based on the split of the M. guatemalae complex into multiple species).
Nonetheless, the
appearance of these birds did not match my expectations based on call. The bird
from Monteverde, as you can see in these photos, is well marked with:
* a well-defined
facial disk (suggests guatemalae
according to the literature)
* prominent black
streaking and cross barring below but not so strongly “vermiculated” (suggests guatemalae)
* prominent
blackish crown streaks (may suggest guatemalae)
* weakly marked
eyebrows (suggests vermiculatus)
* pale, somewhat
greenish bill
The bird from Boca
Tapada shows:
* a relatively
weakly-defined facial disk (suggests vermiculatus)
* finely
vermiculated underparts with little to no black markings (suggests vermiculatus)
* relatively
prominent blackish crown streaks (may suggest guatemalae)
* weakly marked
eyebrows (may suggests vermiculatus
but not clear if relevant in this morph)
* pale,
horn-coloured bill
The physical
features of these birds therefore leave me with some doubts. Of course, the
morphs are not the same so direct comparison is not really possible. In the end
though, the long song of the bird in the Caribbean lowlands versus the short
song of the bird on the Pacific slope suggests to me that the status of the
screech-owls in Costa Rica warrants further investigation and clarification.
This is something that some budding Costa Rican birders and ornithologists
might like to investigate!
Crested
Owl (Lophostrix cristata), pair at day
roost
The unique
(monotypic genus) and spectacular Crested
Owl is always a special treat to observe. In this case, special thanks go
to Jose (Cope) Arte who found this roosting pair of Crested Owls in the Caribbean lowlands of Costa Rica. You will
notice that one of these owls has a cataract in one eye, although that does not
seem to have weakened the pair bond between these two. Although it is very hard
to tell in this particular photo, when observed from two angles, I felt the owl
with the cataract was very slightly larger and hence probably female. The Crested Owl is a widespread, mostly
lowland rainforest species, though sometimes found as high as 2,000 m ASL. The
subspecies found in Central America is L. c. stricklandi. The slight colour
difference between the pair was interesting and when I compare these
individuals to Crested Owls I have
seen in Mexico (click left arrow) they don’t seem to be quite as reddish in the
face. The Central American birds are much darker than birds from Ecuador and
Peru. Some have argued that may warrant a future split since the distribution
is disjunct, with the Amazonian population being separated geographically from the
Central America and northwestern (Pacific) South American birds.
Spectacled
Owl (Pulsatrix
perspicillata)
With thanks again
to Cope Arte, I was delighted to get a chance to see this pair of Spectacled Owls on a day roost.
Spectacled Owl is the largest (can reach 52 cm in length) and most widespread member
of the genus Pulsatrix. This genus is confined to the Neotropics and has only
three species (some authors split Spectacled Owl into two species, giving rise
to a fourth species, but this is not widely accepted). The first photo is a crop showing one more closely to reveal
the exceptionally beautiful pattern and and the second photo shows the
pair together.
Black-and-white
Owl (Strix nigrolineata)
* Taxonomic note:
some authors place this species in the genus Ciccaba
The Black-and-white Owl is one of two
Neotropical species with a unique jet black on white plumage, offset by yellow
bare part colouration (possibly a third species exists, the San Isidro mystery
owl). Black-and-white Owl is found
in Central America (south from southernmost Mexico) and long the Pacific coast
of northern South America (as far south as extreme northern Peru) and east
across northernmost Venezuela. This is a large owl (females can measure as much
as 40 cm in length) with a distinct guttural song. Despite their large size
they seem to consume a lot of invertebrates. This bird came around the lights
of the Laguna Lagarto lodge at night, seemingly looking for moths and perhaps
also bats. Mikkola (2014) states that Black-and-white Owl and Black-banded Owl
“clearly overlap in range in Colombia”; however, examination of range maps from
a variety of sources suggests this is not the case.
Mottled
Owl is a
widespread species (unless you accept the proposed split of the Central
American taxon) that occupies a wide variety of habitats and a considerable
altitudinal range; for example I heard one at approximately 2400 m ASL on
Volcán Irazú. I have found it to be very common in many parts of the
Neotropics, with the possible exception of the Atlantic rainforests of Brazil,
where a disjunct population occurs that seems more thinly distributed. This
bird is more buffy below than others I have photographed in Mexico (possibly a
question of colour morph).
Costa
Rican Pygmy-Owl
(Glaucidium costaricanum), brown and red morphs
The Costa Rican Pygmy-Owl is endemic to the
mountains of Costa Rica and western Panama (rarely as low as 900m ASL but
usually from ~1200 – 3400m ASL). For the most direct comparison I combined two
photos into a collage showing the two colour morphs, red and brown. As
discussed previously (see my previous post on polychromatism), colour morphs
are common in the pygmy-owls (genus Glaucidum)
and this species has two morphs. This taxon is now widely considered to be a
full species; although it was formerly considered to be a subspecies of Andean
Pygmy-Owl (genetic analysis suggests it is more closely related to Mountain
Pygmy-Owl).
Ferruginous
Pygmy-Owl (Glaucidium brasilianum), brown and red morphs
*Taxonomic note:
some authors treat this taxon as Ridgway’s Wood-Owl (Glaucidium ridgwayi)
The Ferruginous
Pygmy-Owl is one of the most widespread of the Pygmy-owls (at least in the
broadest sense as currently recognised by the IOC). In Costa Rica this species
only occurs in the dry northwestern part of the country. This individual was
photographed at Palo Verde in the early morning.
Unspotted
Saw-whet Owl (Aegolius ridgwayi),
Costa Rica
An avian enigma
that is rarely seen, the Unspotted Saw-whet Owl (Aegolius ridgwayi) is a close relative of the Northern Saw-whet Owl
and they have in the past been considered conspecific by some. I was absolutely
delighted to spot the unspotted perched quietly in some liana vines beside a
small road at approximately at 2400 m above sea level near Los Quetzales
National Park, Costa Rica after working hard to try to hear one. Even better, I
got to share my find with some ecstatic Costa Rican birders a couple of days
later. Some taxonomists consider this to be the nominate subspecies, although
others consider this species to be monotypic.
Unspotted
Saw-whet Owl is
the only extant species in the genus Aegolius
from Mesoamerica. In addition there is one species from South America
(Buff-fronted Owl) and two from North America (the Northern Saw-whet Owl and
the Boreal Owl, which in addition to North America also occurs across northern
Eurasia). An additional Caribbean species, the Bermuda Saw-whet Owl (Aegolius gradyi) is now considered
extinct.
One of things I
find most fascinating about the Unspottted
Saw-whet Owl is that their adult plumage is extremely similar to the
juvenal plumage of Northern Saw-whet Owl. Although there are many closely
related bird species pairs where juvenal plumages or female plumages are very
similar, and of course some where all adult plumages are similar, this seems
like a rare case in the avian world where a species’ adult plumage closely
resembles the distinct juvenal plumage of congenitors (making them rather Peter
Pan-like in appearance, i.e. they give the impression of having never grown
up). There are cases of individual birds from different taxa breeding in
juvenal or subadult plumages but the evolutionary mechanism involved in this
case remains unclear.
Thank you!
