Ringing migrant sparrowhawks in southern Thailand.

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BirdingASIA 20 (2013): 37–43 37
The significance of the Thai-Malay Peninsula as a
migratory flyway for raptors and other diurnal
migrants has been recognised since at least the mid-
1980s (Melville & Fletcher 1982, Lekagul et al. 1985,
Bildstein & Zalles 1995). Recent studies (DeCandido
et al. 2004a,b, DeCandido & Nualsri 2009) have
focused on intensive monitoring of the numbers
and species composition of raptors and other
diurnal migrants during both spring and autumn
migrations. From 2001 onwards, observations were
made mainly in the coastal plain near Chumphon
town, at Ban U-Tapao, and at nearby Khao Promsri
as well as a further site, Khao Radar, about 100 km
north of Chumphon town, immediately east of
Highway 4, in Bang Saphan Noi district, Prachuap
Khiri Khan province. Observations at the latter site
have been conducted mainly by the Thai Raptor
Group (Lorsunyaluck et al. 2008, DeCandido et al.
2011).
Since 2008 Khao Dinso, Pathiu district,
Chumphon (10.633°N 99.283°E) has been
recognised as the best site for monitoring the
southward migration of raptors and other diurnal
migrants (Nualsri & DeCandido 2010). Khao Dinso
is a steep, 356 m hill situated about 1.5 km from
the coast. It is deforested but covered with
secondary, regenerating scrub woodland, and offers
spectacular views of the surrounding lowlands (a
mosaic of rubber and oil-palm plantations) and
adjacent sea coast.
Most observations were conducted at 240–300 m
on an east-west ridge (Figure 1). Raptor migration
starts here in mid-August and continues until mid-
November. In the earlier part of the season (until at
least early October) more than 95% of the
individuals on passage are Japanese Sparrowhawks
Accipiter gularis and Chinese Sparrowhawks A.
soloensis (RD & CN pers. obs.). During that period,
migrating raptors tend to hug the coast, skimming
low over the ridges and using them to reduce the
effect of the prevailing south-west monsoon
headwind.
By placing mist-nets (usually five 12 m nets)
along the level part of the ridge-top, siting them
where there were gaps in the tree cover, with the
top of the net no more than 4 m above the ground
and perpendicular to the birds’ flight-line, we were
able to catch small numbers of migrating
FIELD STUDY
Ringing migrant sparrowhawks in southern
Thailand
CHUKIAT NUALSRI, PHILIP D. ROUND, ANDREW J. PIERCE, KASET SUTASHA, DUANGRAT PHOTHIENG,
KRIANGSAK SRIBUAROD, JONATHAN MURRAY & ROBERT DECANDIDO
sparrowhawks. Baiting proved unsuccessful: we
tried small chicks and (for a brief period) Stripe-
throated Bulbuls Pycnonotus finlaysoni suspended
in cages at head-height, but neither appeared to
attract sparrowhawks. All birds trapped were
measured, weighed, examined for moult,
photographed and ringed with numbered metal rings
supplied by the Department of National Parks,
Wildlife and Plants Conservation.
A total of 75 accipiters—48 Japanese
Sparrowhawks (21 adult males, 13 adult females,
10 juvenile males and 4 juvenile females), 26
Chinese Sparrowhawks (10 adult males, 8 adult
females and 8 juvenile males—all the juvenile
Chinese Sparrowhawks were assumed to be males
because their wing-lengths were identical to those
of adult males) and one unsexed juvenile Shikra
Accipiter badius—were trapped during the 2011 and
2012 autumn seasons. Of these, 72 were trapped in
only 10 days (six days in 2011 and four in 2012)
between 19 September and 6 October. Trapping after
the last date was much less successful. Although
Figure 1. Location of Khao Dinso and details of ringing site.
Chumpon Study Centre
Mist-netting area
Observation sala
Walking path
Road
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38 Ringing migrant sparrowhawks in southern Thailand
the overall number and diversity of raptors was
greater at that time, the south-west monsoon
declines in early October and by about 20 October
is replaced by a north-east monsoon tail-wind; the
birds then pass much higher, well beyond the reach
of mist-nets. The numbers of sparrowhawks
passing are much fewer then, and the passage of
other species, especially Black Baza Aviceda
leuphotes and Grey-faced Buzzard Butastur indicus,
increases.
The numbers of hawks trapped increased as the
day progressed, peaking during the second half of
the afternoon (Figure 2). Although the reduced
capture frequency in the middle part of the day and
the early afternoon corresponded with fewer
sightings over the coastal ridge, this did not
apparently indicate a real decline in numbers but
rather a shift in flight pattern. As updrafts became
stronger in the hottest part of the day, birds tended
to be higher and were both harder to catch and less
visible, whilst the passage tended to be further to
the west at that time (RD pers. obs., M. Siponen
pers. comm.). Nevertheless, low clouds and sudden
rainstorms brought birds lower, leading to capture
at any time of day.
Adult and second calendar-year males
accounted for 43.8% of Japanese Sparrowhawks
and 38.5% of Chinese Sparrowhawks trapped.
Juvenile male Japanese Sparrowhawks also
outnumbered juvenile females, whilst no juvenile
female Chinese Sparrowhawks were identified.
Sexual size dimorphism was far more obvious in
Japanese than Chinese Sparrowhawks and there
was some overlap in wing-length between the
largest adult males and smallest adult females of
the latter species (Table 1). Since the mean and
standard deviation of the wing length of our
juvenile sample was identical to that of adult males,
we may be reasonably confident that no juvenile
females were overlooked.
Because we were not baiting to attract raptors,
we may assume that the body mass and age
composition of our trapped birds were probably
representative of the migrating population.
Baiting, widely used elsewhere for raptors, in
combination with various other trapping methods,
may have a tendency to bias catches according to
age ratio or physical condition, since lighter or more
emaciated birds may have a greater need to feed
(Nass 1964, Weatherhead & Ankney 1984, Gorbay
& Yom-Tov 1994). Roughly 20% of the Japanese
Sparrowhawks handled had distended crops,
indicating they had recently fed, and they were
occasionally observed harrying and hunting small
birds. We did not observe Chinese Sparrowhawks
actively hunting, although their feeding habits,
which, at least in breeding and wintering areas,
involve short flights to capture frogs or insects from
the ground or wetland margins (Ferguson-Lees &
Christie 2001), may be less easily detected.
Nevertheless, we have once, elsewhere on north-
bound spring migration, observed a Chinese
Sparrowhawk preying on birds. Although we
speculated that Chinese Sparrowhawks might feed
less on migration than Japanese Sparrowhawks,
and rely more on fat reserves to fuel their migration,
we could not detect significantly elevated levels of
body fat among any of the sparrowhawks that we
handled.
Chinese Sparrowhawk males were, on average,
about 88% of the body mass of females, while
Japanese Sparrowhawk males were much smaller,
roughly two-thirds the body mass of females (Table
1). Although juveniles tended to be lighter than
Table 1. Wing length and weight of Accipiter species trapped at Khao Dinso during autumn migration in September and
October 2011 and 2012.
Age/sex class Wing (mm) Range (n) Weight Range (n)
A. gularis ad f 194.5 ± 3.00 189–200 (12) 152.2 ± 12.97 115.6–167.8 (13)
A. gularis ad m 167.2 ± 4.06 161–178 (21) 100.9 ± 7.73 88.8–118.4 (21)
A. gularis juv f 190.3 ± 1.71 188–192 (4) 142.8 ± 6.60 135.6–151.3 (4)
A. gularis juv m 165.5 ± 3.75 163–170 (10) 95.3 ± 7.94 84.8–108.1 (10)
A. soloensis ad f 199.4 ± 5.24 190–204 (4) 137.5 ± 8.94 124.9–150.1 (8)
A. soloensis ad m 192.1 ± 4.33 183–199 (10) 121.0 ± 8.21 106.7–138.3 (10)
A. soloensis juv all 192.1 ± 4.33 183–199 (8) 118.0 ± 8.94 105.8–129.5 (8)
Figure 2. Numbers of Japanese Accipiter gularis and Chinese
Sparrowhawks A. soloensis trapped in relation to time of day.
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BirdingASIA 20 (2013) 39
adults of the corresponding sex in both species,
these differences were not statistically significant
(t-test).
Almost all the non-juvenile sparrowhawks
trapped displayed arrested moult, having replaced
some inner primaries. In general, moult (Figure 3)
had progressed further in Chinese Sparrowhawks
(median number of new, moulted primaries = 5,
range 3–10) compared with Japanese Sparrowhawks
(median number of new primaries = 2, range 0–
5). Herremans & Louette (2000) noted arrested moult
in an October-taken Chinese Sparrowhawk
specimen from Thailand.
Male Japanese Sparrowhawks and both sexes
of Chinese Sparrowhawks that were one year old
(second calendar-year birds) could be recognised
because their retained (unmoulted) primaries were
barred, brown juvenile feathers. There was
considerable variation in the iris colour of males.
Japanese Sparrowhawks in apparently definitive
adult male plumage showed irides that ranged from
orange-scarlet to uniform crimson-red, with a
yellowish outer ring (Plates 7 & 8). The iris colour
of adult male Chinese Sparrowhawks was dark
vinous-crimson (Plate 1) but a second calendar-
year male had a red iris with a yellow-flecked outer
ring (Plate 2). Juveniles and females of both species
had yellow irides.
In addition to raptors, Khao Dinso has
significant potential for studying a range of other
migrant species. The most abundant landbird
migrants trapped were Eastern Crowned Warblers
Phylloscopus coronatus and the long-distance
migrant race of Asian Paradise-flycatcher
Terpsiphone paradisi incei. Further ringing activities
have the potential to reveal scarce or little-known
species and add further to knowledge of the
seasonality of migration. We have already trapped
six Alström’s Warblers Seicercus soror, a species
hitherto known from the Thai-Malay Peninsula only
by a single sight record (Wells 2007).
The site is principally productive for monitoring
the southward raptor migration. It is unlikely that
our capture success in early autumn can be
repeated during spring migration since the
northward migratory flight-line largely bypasses
Khao Dinso, being shifted several km to the west.
Northbound migrants are usually assisted by a
south-west tail-wind and are higher and harder to
capture. Nonetheless, it would be desirable to
maintain some ringing and monitoring effort at
Khao Dinso year round, especially for other
landbird migrants.
Ringing and monitoring work will be continued
in future seasons alongside the visual recording of
raptor passage and other diurnal migrants. We will
possibly attempt a greater range of capture
techniques and, if funds allow, fit satellite
transmitters to track the migration of
sparrowhawks. A permanent study centre, intended
as an observatory for study of all avian migrants
Figure 3. Extent of replacement of primaries in adult and
second calendar-year Japanese Accipiter gularis and Chinese
Sparrowhawks A. soloensis.
Plate 1. Adult male Chinese Sparrowhawk Accipiter soloensis
showing dark vinous iris. Note the bright orange-yellow cere
and grey orbital ring which are common to all age/sex classes.
19 September 2012.
Plate 2. Apparent Second calendar-year male Chinese
Sparrowhawk showing bi-coloured iris, 19 September 2012.
P. D. ROUND
P. D. ROUND
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40 Ringing migrant sparrowhawks in southern Thailand
Plate 3. Apparent second calendar-year female Chinese Sparrowhawk ventral view, 22 September 2012.
Plate 4. Apparent second calendar-year female Chinese Sparrowhawk dorsal view. Note retained old, unmoulted two outermost
primaries and some secondaries. The left central tail feather is also old and unmoulted. 22 September 2012
P. D. ROUNDP. D. ROUND
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BirdingASIA 20 (2013) 41
Plate 5. Juvenile Chinese Sparrowhawk. Note the grey orbital ring and bright orange-yellow cere which are shared by all age/sex
classes. 21 September 2012.
Plate 6. Juvenile Japanese Sparrowhawk A. gularis. Note the yellow orbital ring and greenish-yellow cere shown by all age/sex
classes. 21 September 2012.
P. D. ROUNDP. D. ROUND
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42 Ringing migrant sparrowhawks in southern Thailand
including raptors, was built on the lower slopes of
Khao Dinso in October 2012 by the Pathiu district
administration, with funding from Chumphon
province. Since nature education and awareness
promotion are major goals of the centre, interested
members of the public, school groups, university
undergraduates, etc. may also be invited to observe
the ringing activities in future.
Acknowledgements
We thank Pinit Charoenpanit, former Chumphon
province governor, Prasit Fugudom, Pathiu district
chief officer and Jareak Kosin, headman and his
assistant in village no. 8, Bangson subdistrict, for
their kind support and assistance. This work was
carried out with permission from the Department
of National Parks, Wildlife and Plants Conservation
who also supplied the bird rings. Wangworn
Sankamethawee and Martti Siponen assisted with
ringing. We thank Keith Bildstein for his helpful
comments and suggestions on our data. We are
grateful for contributions to funding in 2012 made
through Baan Suksabye, continuing a tradition of
giving by Nurak Israsena and Edmund W. Pease.
Perawit Insuan prepared the map. Philip Round is
supported by The Wetland Trust UK.
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Chukiat NUALSRI
Nathung Administrative Organisation, 99 Mu3
Nathung Sub-District
Muang Chumphon 86000, Thailand
Email: bnternstar@gmail.com
Philip D. ROUND
Department of Biology, Faculty of Science
Mahidol University, Rama 6 Road
Bangkok 10400, Thailand
Email philip.rou@mahidol.ac.th
Plates 7 & 8. Variation in iris colour in apparent adult male Japanese Sparrowhawks, 19 September 2012 (Plate 7), 25 September
2011 (Plate 8).
P. D. ROUND
P. D. ROUND
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BirdingASIA 20 (2013) 43
Andrew J. PIERCE
Conservation Ecology Program
School of Bioresources and Technology
King Mongkut’s University of Technology Thonburi
Bangkhunthien, Bangkok 10150, Thailand
E-mail: andyp67@gmail.com
Kaset SUTASHA
Veterinary Teaching Hospital
Faculty of Veterinary Medicine
Kasetsart University, Bangkok 10900, Thailand
Email: kasetvet57@gmail.com
Duangrat PHOTHIENG
Director, Captive Propagation Division
Department of National Parks, Wildlife
and Plants Conservation
Bangkok 10900, Thailand
Email: pothieng@hotmail.com
Kriangsak SRIBUAROD
Khlong Saeng Wildlife Research Station
Department of National Parks, Wildlife
and Plants Conservation
P.O. Box 15, Khao Phang, Ban Tha Khun District
Surat Thani 84230, Thailand
Email: JOKSWRS@hotmail.com
Jonathan MURRAY
195 Soi 19 Pradipat Rd, Bangkok 110400, Thailand
Email: jmurray808@yahoo.com
Robert DECANDIDO
1831 Fowler Avenue, The Bronx
New York 10462, USA
Email: rdcny@earthlink.net
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