Spot-winged Thrush Zoothera spiloptera is an endemic species
recorded primarily in the wet zone forests and adjoining well wooded
habitats of Sri Lanka. It occurs from the lowlands up to 2100 m. Localised
populations also exist in the riverine forests of the dry zones (Grimmett
et al. 2000, Clement and Hathway 2000, Rasmussen and Anderton
2005). It is rather shy except at dawn and dusk (Grimmett et al.
2000, Rasmussen and Anderton 2005), when it calls frequently from
a low perch and often comes into the open on forest foot paths, etc
(Grimmett et al. 2000). Much of its daytime is spent foraging
on the ground in the forest interior and as a result it could easily
be overlooked especially when it is not singing (Clement and Hathway
2000). Due to these habits photography of the species is quite challenging
as it is often encountered when the lighting is not all that conducive.
In this note I record a nest of Spot-winged Thrush in Sinharaja World
Heritage Site Reserve (hereafter referred as Sinharaja), and offer
a few notes on its plumage with particular reference to its undocumented
postocular bare skin patch and speculate its possible function as
a pseudo-bill to create an anti-predator “shadow face”.
Plate 1-3 & 6
Nest of Spot-winged Thrush Zoothera spiloptera, Sinharaja
World Heritage Reserve, Sri Lanka, 29 September 2004.
Plates 4 & 5. Spot-winged Thrush Zoothera spiloptera
Kelani Valley Forest Reserve, Kithulgala, Sri Lanka, 23 January 2005.
On the 29 September at around 14h30 while birding alone in Sinharaja,
I observed a nest of Spot-winged Thrush in the forest interior. It
was built 2 m from the ground in a Lijndenia capitellata
tree (Family: Melastomaceae, local name: Pinibaru) in the
forest understorey close to a stream. I was about 5 m from it when
I first discovered it. I went back a few steps to observe it unobtrusively.
I noticed both parent birds attending to the nest: bringing food and
brooding. I obtained a few digiscoped pictures of this behaviour.
When both parents vacated the nest to forage, I photographed the nest
contents, which consisted of two hatchlings. As reported in the literature
(Legge 1880, Henry 1998, Harrison 1999, Samaraweera 2004, Rasmussen
and Anderton 2005), the nest was very well camouflaged and looked
like an untidy aggregation of sticks & dead leaves, etc., from
outside, but its interior was a neat cup lined with rootlets and tiny
twigs. After a few minutes I vacated the place. I did not visit the
nest site until October 2004 when I bserved one fledged juvenile Spot-winged
Thrush, which looked very much like the adult. It was seen in association
of two adult birds and I observed it being fed by one of them.
Notes on the plumage of Spot-winged Thrush
The following notes on the plumage are based on subsequent analysis
of the photographs I took of the adult birds at the above nest (Plate
1, 6) and another individual photographed in a home garden close
to the Kelani Valley Forest Reserve, in Kithulgala on 23 January
2005 at 11h40 (Plate 4-5).
Forehead crown and nape olive brown. Bill black with indistinct
pale gape. Tiny indistinct black hiskers around the base of bill.
Lores whitish. Eye dark. Diffuse black malar stripe and whitish
submustaial stripe. Chin and throat white. Broad vertical black
stripe below the eye. Small black patch on top left of the eye,
which combines with darker eye to give the bold vertical black stripe
below it a longer appearance especially when viewed from a distance.
Prominent white eye-crescent on the rear portion of the eye starting
halfway above it and continuing down till it reaches the bold vertical
black stripe below it, giving impression of a broken white eye-ring
when viewed laterally. Ear coverts whitish. A very distinct triangular
dark post-ocular bare skin patch (hereafter “postocular patch”),
with a tiny black line above it and diffuse black stripe below it
(forming the rear edge of the ear coverts). These later two features
merging with it to create a black crescent-like appearance behind
the eye when viewed from any distance. Tiny series of white spots
around postocular patch and black stripe below it demarcating that
area. The olive-brown upperparts shade into a thin diffuse olivaceous-grey
line around the facial area. This begins as a thin line from billbase,
going above the black and white borders of the upper eye and gradually
becoming broader as it goes around the outer borders of the tiny
white spots behind the eye and getting still broader on necksides
down to flanks. A few tiny indistinct hair-like feathers (filoplumes)
Mantle, scapulars and lesser wing-coverts olive brown becoming browner
across lower back, rump and uppertails coverts. Median coverts black,
tipped white. Greater coverts blackish-brown and tipped with smaller
white spots than median coverts. Tertials almost uniform warm brown
with darker fringes. Tail warm brown. Breast, belly and flanks white,
heavily marked with black fan-shaped spots. Flanks washed with diffuse
olivaceous-grey. Lower belly and vent area whitish and unmarked.
Legs and feet flesh coloured with grey hue. Claws pale.
Rasmussen and Anderton (2005) the breeding of Spot-winged Thrush
mainly takes place in
According to March to May and August to December in the north. Kanchana
Weerakoon who carried out a single species study of Spot-winged
Thrush in 2000, has observed breeding activity in September, October
and November in Sinharaja and a nearby forest patch (pers.com).
This information and my nest record from September indicates that
the northern breeding season of August-December is also valid for
Sinharaja in the south.
The post ocular patch has not been mentioned in the literature.
K. Weerakoon noticed it in the mist netted birds and specimens lodged
in the National Museum of Sri Lanka but could not assign a possible
reason for it (pers.com). I inquired from various other sources
about it but none seemed to be even aware of the presence of this
feature in Spot-winged Thrush or the possible function of this feature
in birds in general.
When seen from the rear (Plate 5) the post ocular patch creates
the impression of a pseudo-bill, in the post ocular region. Its
triangular shape and the small white surrounding dots help to highlight
it clearly. Also in the rear view the white eye-crescent on the
rear eye-ring helps the eye to stand out prominently. These two
features combine to create an impression of an ‘eye and bill’
and therefore a “shadow-face” around the postocular
region, which may function to fool an ambushing predator planning
an attack from behind. Since ambush predators attack unsuspecting
prey at close range, it may be that the sight of this shadow-face
can confuse an ambushing predator for an instant, just long enough
for the intended prey to make a getaway.
The colour of this pseudo-bill matches that of the actual bill
closely. This is true for most other species which bear this postocular
patch. The bird species in which the post ocular bare patch is pronounced
are mostly terrestrial or semi-terrestrial. A further function of
this patch may also to give the bearer a wider area of view on the
sides of the head in addition to enabling the eye to gather more
light in poorly lit conditions. Thus the postocular patch may confer
several important survival advantages.
Prof. Sarath W. Kotagama for commenting on the manuscript. I would
also like to
I would like to thank thank for Kanchana Weerakoon for sharing her
knowledge about Spot-winged Thrush.
Clement, P and Hathway, R. (2000) Helm Identification Guides: Thrushes.
London: Christopher Helm (Publishers) Ltd.
Grimmett, R., Inskipp, C. and Inskipp, T (1998) Birds of the
Indian Subcontinent. New Delhi: Oxford
Henry, G.M. (1998) A Guide to the birds of Ceylon. Third
edition. New Delhi: Oxford University Press. 1st edition in 1955.
Legge, W.V (1983) A History of the Birds of Ceylon. Dehiwela:
Tisara Prakasakayo. 1st edition in 1880.
Rasmussen, P.C. and Anderton, J.C. (2005) Birds of South Asia.
The Ripley Guide. Vols 1 and 2.
Smithsonian Institute and Lynx Edicions, Washington, D.C and Barlelona.
Samaraweera, P (2004) In: Ceylon Bird Club Notes: 65
Amila Salgado, Wildlife Tour Leader, 146D, Ekanayake Niwasa,
Bomiriya, Kaduwela Sri Lanka. Email:
The above article
was originally published in BirdingAsia 4 December 2005, the new-look
Oriental Bird Club.