Observations on the nesting of the Large Frogmouth Batrachostomus auritus in Taman Negara National Park, peninsular Malaysia

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BirdingASIA 14 (2010): 37–43 37
FIELD STUDY
Observations on the nesting of the Large
Frogmouth Batrachostomus auritus in Taman
Negara National Park, peninsular Malaysia
TAN GIM CHEONG & YONG DING LI
Introduction
The aptly named Large Frogmouth Batrachostomus
auritus is the largest Asian frogmouth and possibly
the least frequently recorded of the three species
occurring in the Malay peninsula. It is currently
listed as globally Near Threatened (BirdLife 2010)
given its dependence on lowland dipterocarp forest,
a rapidly disappearing habitat in Sundaic South-
East Asia (Lambert & Collar 2002). Wells (1999)
described it as a specialist of plains-level forest and
all recent records have indeed originated from the
lowlands, particularly the Taman Negara National
Park in peninsular Malaysia, most of which lies at
elevations below 305 m (Yeap et al. 2007).
Elsewhere in its range there are few recent records
except from Way Kambas National Park in southern
Sumatra where it is still regularly recorded (Olay
& Simay 2007) and, occasionally, from Danum
Valley and Gn Mulu National Park, both in northern
Borneo (Holyoak 1999, Smythies 1999). In
peninsular Malaysia, it is regularly seen in parts of
the Krau Game Reserve (F. R. Lambert in litt.) and
was formerly recorded in the well-studied Pasoh
Forest Reserve, Negri Sembilan (Wells 1999), but
there are no recent records.
There are three known recent nest records, one
from Taman Negara in 2006 (Wright 2009) and
two from Way Kambas in July 2007 (J. Olah in
litt.) and July 2008 (J. Eaton in litt.). All three
records referred to single unsexed adults at the nest,
although Eaton noted the presence of a chick.
However, various aspects of the nesting cycle,
including incubation, fledging period and parental
care, are still largely unknown (Holyoak 2001) and
the chick of this species is hitherto undescribed
(Cleere 2010). Here we report on observations made
at a nest of a Large Frogmouth in Taman Negara
and present the first photographic images and
description of the chick of this little-known species.
Our observations were made over a ten-week
period from 14 February, when a nest was first
suspected, to 26 April 2010.
Description of the nest
The nest was located in a rather poorly concealed
position 4 m above the ground and about 30 m
from a river in primary lowland dipterocarp forest
at an elevation of about 120 m (Plate 1). The nest
was an estimated 7–8 cm in diameter and was built
in the fork of a horizontal branch (about 5 cm thick)
and a thinner branch. It was a cup-shaped platform
partly enveloping the horizontal branch as well as
the base of the thinner branch on which it rested
(Plate 2). In the early part of the observation period,
there were small fresh green leaves as well as dried
leaves on the nest, which together formed the bulk
of the structure. There also appeared to be a fine
layer of dark silk-like material around the exterior
of the nest, and this is likely to have originated
from the adult’s feathers, which are known to be
regularly used in the nests of a number of
Batrachostomus species. As the nest was relatively
small and compact, the adults had to perch next to
it when feeding the chick.
Plate 1. Nesting environment of the Large Frogmouth
Batrachostomus auritus, Taman Negara NP, Malaysia, April 2010.
ALL PHOTOS BY TAN GIM CHEONG

38 Observations on the nesting of the Large Frogmouth Batrachostomus auritus in Taman Negara NP, peninsular Malaysia
Description of the chick
We first observed the chick when it was 2–3 days
old (20 March). It appeared to be very similar to
that of other Batrachostomus frogmouths, being
entirely covered with fine white down (Plate 3),
although at the time of observation we noted that
flight feathers had started to develop on the wings.
When the chick was about 15 days old (2–3 April),
most of its white down had already been replaced,
remaining only on parts of the head and throat,
whilst both upperparts and underparts were
covered in brown feathers. The flight feathers were
completely developed and starting to show
patterning typical of the adults.
Plumage differences between the adult
frogmouths
Although we were unable to sex the adults
definitively, there were noticeable differences in
plumage, suggesting limited sexual dimorphism
(Plate 4). Comparison of photographs taken on each
visit revealed that it was always the same individual
present at the nest during daylight hours (the ‘day-
shift’ parent). This bird was the more strongly
marked of the adult birds and had white spots edged
with little or no black on the upperwing-coverts,
giving them a distinctly triangular appearance. The
second adult (the ‘night-shift’ parent) had clearly
smaller, more teardrop-like white spots, edged with
much more black. On the scapulars, the ‘day-shift’
parent had black subterminal spots with buff tips
whereas the ‘night-shift’ bird had larger and more
prominent black spots. We also noted that the ‘day-
shift’ adult possessed more well-defined pale buff
brows and darker inner webs to the primaries, which
appeared blackish rather than brownish. Given that
Plate 2. Large Frogmouth at nest, with one wing resting on a thin branch, Taman Negara NP, Malaysia, 20 March 2010.
Plate 3. Large Frogmouth chick at 2–3 days old, Taman Negara
NP, Malaysia, 20 March 2010.

BirdingASIA 14 (2010) 39
females may be plainer and duller (Cleere 2010), it
is likely that the ‘night-shift’ bird was the female.
Chronological summary of observations
14 February
An adult Large Frogmouth was first observed at
18h30 by YDL, perched on a branch of an
unidentified tree. The bird was observed until
19h00 and again from 23h00 to 23h45. It seemed
to remain in the same spot and in an unchanged
position over that time, leading us to believe that
it was possibly nesting, although we were unable
to make out any nest structure.
15 February
Observations were made sporadically from 11h00
to 15h00. The bird was in almost the same position
as the previous evening. We noticed small bits of
dried vegetation sticking out from the bird’s breast
feathers and closer examination showed that this
was actually the lower part of the nest structure,
much of which remained concealed under the bird.
We inferred from its behaviour that the bird was
actively incubating.
25 February
Observations were made from 08h30 to 14h30. An
adult was present at the nest during the entire period,
Plate 4. Large Frogmouth, comparison of ‘day-shift’ parent (left) and ‘night-shift’ parent (right), both with chick, Taman Negara NP,
Malaysia, 2–3 April 2010. Note the subtle but clear plumage differences.
Plate 5. Rear view of Large Frogmouth on nest, Taman Negara
NP, Malaysia, 25 February 2010.

perched lengthwise along the nest branch, with its
tail towards the tree trunk (Plate 5). In this position
it resembled a clump of dead leaves. When a wild
pig Sus scrofa and a squirrel Callosciurus sp. passed
close by, the frogmouth opened its eyes and slowly
turned its head to look. When each animal
approached within 10 m, the bird slowly tilted its
head up, keeping its eyes marginally open to monitor
potential disturbance. We did not observe any
discernible compression of the bird’s body to adopt
the ‘broken branch’ or freezing posture, in contrast
to the behaviour of other frogmouths, particularly
the Australian Frogmouth Podargus strigoides, when
alarmed (Holyoak 1999).
28 February
Observations were made briefly from 02h00 to
02h30, and from 15h00 to 15h45. A bird was still
on the nest. During the later visit, a pair of vocal
Black Magpies Platysmurus leucopterus came very
near to the nest, alarming the incubating bird
sufficiently to open its eyes completely, but it
resumed its normal position once the visitors left.
20 March
Observations were made 18h00 to 20h15, sunset
being around 19h15. We noted that a few belly
feathers of the sitting ‘day-shift’ adult shuffled for
40 Observations on the nesting of the Large Frogmouth Batrachostomus auritus in Taman Negara NP, peninsular Malaysia
Plate 6. Large Frogmouth opening its mouth to cool down after 10 minutes of exposure to direct sunlight, Taman Negara NP,
Malaysia, 25 February 2010.
a few seconds, although it was not clear if these
movements originated from the adult or a concealed
chick. We subsequently observed the ‘night-shift’
adult perched beside the nest, which was now
exposed, revealing a single downy chick. The chick
was estimated to be 2–3 days old and was covered
in white downy feathers, similar to those of other
frogmouth species (Jayarathna 2004) but it had also
started to develop flight feathers on its wings.
The ‘night-shift’ adult brought back a relatively
large, unidentified green insect, possibly a mantid,
and fed it to the chick, which struggled to swallow
it. Even before the chick had fully ingested the prey,
the adult repositioned itself over the nest and
covered the chick. After about 20 minutes, the adult
looked around briefly before flying off.
Subsequently, the ‘day-shift’ adult returned with a
large brownish, unidentified arthropod. This was
quickly fed to the chick and again the adult
proceeded to position itself over the nest, covering
the chick once more.
2–3 April
The nest was monitored with an infra-red sensitive
video camera continuously from before sunset on
2 April to the morning of 3 April. On our arrival at
the site at 18h00, the adult on the nest was
identified as the ‘day-shift’ bird. The chick was now

BirdingASIA 14 (2010) 41
approximately 15 days old and filling the nest. Most
of its white down had been shed: only the throat
and parts of its head remaining white. The
underparts were covered with brown feathers and
the flight feathers showed patterns typical of the
adults, although the tail was notably short. It
exercised its wings vigorously from time to time,
even forcing the brooding adult to flap its wings to
maintain balance. When looking at the observers,
the chick would sometimes move its head side-to-
side in the manner typical of owls.
At 19h30, while the chick was still flapping its
wings, the adult flew off. Seven minutes later the
same adult returned to the nest with food for the
chick. After several minutes it flew off again and
returned about 14 minutes later with a relatively
large brown insect, which proved too large for the
chick to eat. After several unsuccessful attempts,
the adult ate the insect itself. At 20h31, the ‘night-
shift’ adult flew in and perched next to its brooding
partner. This was the first time both adults had
been seen at the nest together, although the ‘day-
shift’ adult flew away 10 seconds later. The ‘night-
shift’ adult did not bring any food for the chick
and appeared just to be taking over brooding duties.
At 21h35, the ‘day-shift’ adult returned and both
adults remained together for a while. Then the ‘day-
shift’ bird took over the nest duties. Through the
course of the night the chick was fed a total of six
times, half of which occurred within the 70 minutes
before dawn. One prey item was a stick insect, part
of which was fed to the chick while the adult ate
the remainder. This adult then repositioned itself
back at the nest where it remained until
observations ended at 08h35.
25 April
We arrived at the nest site at 19h50 and found the
nest empty. After some searching, the ‘night-shift’
adult was located nearby, perched on a bare
horizontal vine with its wings partially spread,
apparently attempting to dry itself. The chick and
‘day-shift’ adult were not observed at all.
26 April
Observations were made over a rainy morning and
afternoon. The nest site was visited at 09h00 but
no birds were found. When revisited at 11h05, the
family of three were perched snugly together on a
drooping branch about 20 m from the nest. The
chick was visibly smaller than its parents and was
perched between them. From 12h50 to 14h30, all
three birds remained largely in the same position
with the chick still occasionally exercising its wings.
We estimated it to be about 20 cm long—slightly
more than half the length of the adults. Its
underparts were the same chestnut brown as the
adults but lacked the white spots, as did the
upperwing-coverts, whilst its primary and tail
feathers were barred like those of the adults.
Discussion
Little was previously known about the nesting cycle
and parental care of the Large Frogmouth and,
Plate 7. Large Frogmouth 15-day-old chick with ‘night shift’
parent, Taman Negara NP, Malaysia, 3 April 2010.
Plate 8. Large Frogmouth, view of 15-day-old chick, Taman
Negara NP, Malaysia, 2 April 2010.

42 Observations on the nesting of the Large Frogmouth Batrachostomus auritus in Taman Negara NP, peninsular Malaysia
although we could not be present daily, our
observations allowed us to make a number of
inferences about the breeding biology of the
species. The nest was discovered on 14 February
and the chick first seen on 20 March, when it was
already roughly 2–3 days old. It is assumed that
only one egg was laid. If the egg was laid around
14 February and the chick hatched on 18 March,
the incubation period was 32 days (more if the egg
was laid earlier). By the time of our final visit on
the 25 and 26 April, the chick had left the nest.
This indicates that the chick took somewhere
between 20 and 38 days to fledge.
The consistent, temporal partitioning of
brooding duties is probably the first reported for
the Large Frogmouth, although we were unable to
sex the adult birds confidently despite noticeable
plumage differences. While it is claimed that the
male incubates during the day and the female at
night, Holyoak (2001) suggested that this could just
be speculation inferred from the behaviour of
closely related species and is thus not entirely
certain. Of the few specimens that have been
sexed, most appear to be males and information
on the female plumage is still lacking. There are
no diagnostic differences in plumage which
allow observers to identify the sex of birds
confidently.
During our observations, we noted that the
brooding adult would sometimes wait for its partner
to fly in and perch beside the nest before leaving it.
At other times, it would start to look around for
reasons unclear to us before flying off. Shortly after,
the second adult would fly in to assume nest duties.
We were unable to tell if sight, soft vocalisations or
any other means were used to detect the approach
of the other adult. Indeed, we did not notice any
vocalisations during the entire period of observation.
We used a tape playback at the end of the period
but this did not elicit any response from the birds
although they were clearly present nearby.
The nest structure we have described seems to
be very similar to those of the nesting birds on
Sumatra in 2007 and 2008 (see OBI at http://
www.orientalbirdimages.org). It appeared to be
made largely from plant matter, especially dried
leaves, with smaller amounts of down. This
contradicts Robinson & Chasen (1936), who
described a nest from Sarawak as being a small
circular pad of closely matted down, and a
description in Robson (2002). On the other hand,
our description of the nest together with the
Sumatran records sets it apart from the descriptions
of nests of a number of other smaller Batrachostomus
frogmouths, which are mostly composed of down
(Holyoak 1999, Wells 1999, Jayarathna 2004).
Plate 9. Large Frogmouth, adults with 38-day-old chick, Taman Negara NP, Malaysia, 26 April 2010.

BirdingASIA 14 (2010) 43
There are two previous nesting records in
peninsular Malaysia from Kota Tinggi, Johore
(Wells 1999) and Taman Negara (Wright 2009);
our record here represents the third and most
complete documentation of nesting for this species
in the Malay peninsula and possibly its entire range,
presenting previously unknown details of parental
care and general nesting phenology.
Acknowledgements
TGC would like to thank to Felix Wong and Ben
Lee for company in the field, especially during night
observations. YDL thanks Bert Harris, Brett
Scheffers and Lim Kim Chuah for company in the
field. We are grateful to Frank Lambert, Nigel Cleere
and Robert Hutchinson for their invaluable
comments on the manuscript.
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Tan Gim Cheong
Nature Society (Singapore) Bird Group,
510 Geylang Road, #02-05, The Sunflower,
Singapore 389466
Email: ellebtxt@yahoo.com
Yong Ding Li
South-east Asian Biodiversity Society,
504 Choa Chu Kang Street 51, #01-173,
Singapore 680504
Email: zoothera@yahoo.com