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INTRODUCTION
Fifty-five species of diurnal raptors occur in Thailand,
of which 41 undertake partial or long-distance
movements within or through the country (Zalles and
Bildstein 2000, Robson 2002). Thailand is an impor-
tant migration crossroads for east Asian raptors that
over-winter in Malaysia, Singapore, Bali, Sumatra, and
elsewhere in Indonesia. Since the 1960s, biologists
have looked for areas on the Thai-Malay Peninsula
from which to count migrating raptors. Most prior
research comes from field studies in Malaysia
(Medway and Nisbet 1965, Wells 1990, Wells 1999).
Raptor migration in Thailand remains largely undocu-
mented (see Melville and Fletcher 1982, Lekagul et al.
1985, Bijlsma 1996).
In September 1997, large numbers of migrating
raptors were observed by C. Nualsri near the town of
Chumphon, south-east Thailand (Fig. 1). Subsequent
observations confirmed significant movements of
raptors through the region each autumn. This impor-
tant coastal-plain bottleneck in peninsular Thailand
had been previously recognised from observations
made approximately 100 km north of Chumphon by
Melville and Fletcher (1982) and by P. D. Round and
others in 1983–1994 at Kui Buri, c.5 km east of Ban
Yang Chum near the Gulf of Thailand (see Zalles and
Bildstein 2000). This apparently important flyway has
not been well studied, however, and the relative
numbers of raptors using it in spring and in autumn,
the origin of the migrants, and their ultimate destina-
tions, are all largely unknown (Lane and Parish 1991,
Zalles and Bildstein 2000, Nijman 2001a).
In 2003, we conducted a six-week count to deter-
mine the phenology of these movements including the
numbers of species and individuals involved, together
with the daily and seasonal timing of the migration.
METHODS
Chumphon (10
o
28
’
N 99
o
13
’
E; sea level) is a town
(population: 16,000) on the eastern coastal plain of
southern Thailand, 460 km south-west of Bangkok,
FORKTAIL 20 (2004): 49–54
Autumn 2003 raptor migration at Chumphon,
Thailand: a globally significant raptor
migration watch site
ROBERT DECANDIDO, CHUKIAT NUALSRI, DEBORAH ALLEN and
KEITH L. BILDSTEIN
Daily counts of migrating raptors were made on 43 days between 27 September and 9 November 2003 near the city of Chumphon
in south-east Thailand. Overall, 170,665 migrating raptors of 15 species were counted during 378 hours of observation (452
birds/hour).The counts of five raptor species (Black Baza Avecida leuphotes,Oriental Honey-buzzard Per nis ptilorhyncus, Eastern Marsh
Harrier Circus spilonotus, Chinese Sparrowhawk Accipiter soloensis and Grey-faced Buzzard Bustatur indicus) represent some of the
highest totals reported to date. Winds from the north to west and cloud cover were positively associated with the number of raptors
seen. We recommend that counts be continued at Chumphon in the future and that the site is used to promote raptor conservation
in Thailand.
Figure 1. Location of Chumphon, Thailand (1) relative to
other important migration watch sites in East Asia: Beidaihe,
China (2); Uchiyama-toge, Nagasaki, Japan (3);
Kohyamacho, Kagoshima, Japan (4); Miyako Islands
(Ryukyus), Okinawa, Japan (5); Selangor Plain, Malaysia (6);
and Bali Barat National Park, Indonesia (7).
Forktail 20 (2004)
550 km north of Malaysia, and 55 km east of
Myanmar. The north-south Bilauktaung range of
mountains 35 km to the west funnels many diurnal
bird migrants through this 30-km wide coastal plain
adjacent to the Gulf of Thailand (Wells 1999, Zalles
and Bildstein 2000). Migration was observed at a site
(10
o
28.40
’
N 99
o
13.26
’
E) in an unprotected freshwater
marsh 4.6 km east-north-east of Chumphon, and
approximately 2 km north-east of the coastal highway
at Ban U-Tapao,Tha Yang subdistrict, Muang district,
Chumphon province. The marsh is composed prima-
rily of emergent aquatic plants, including sedges Carex
spp., cat-tails Typha spp., and common reed Phragmites
australis.Vegetation averages less than 1.5 m high, and
it does not prevent observation of low-flying raptor
migrants. On fair days, it is possible to see 10 km to the
north-east, 3 km to the east and west, and about 1 km
to the south.
The weather in late summer–early autumn is deter-
mined by the interaction between a monsoonal
low-pressure system in the Pacific Ocean to the east,
and a high pressure system in the Andaman Sea to the
west. In September and early October, the high
pressure system prevails, and most winds are from the
west or north-west. By mid-October, the low pressure
system predominates, and winds are easterly. Heavy
rain is common in mid-October as low pressure
replaces high pressure in the region. The bulk of the
migration occurs during the ‘south-west’
(April–October) rather than ‘north-east’ monsoon
(November–January).
We counted migrants from 27 September to 11
November, which correspond to the peak of the raptor
movements in the area. Migrating raptors were
counted by RDC using 10x binoculars, assisted at
times by CN and DA. Count protocols followed those
described in Bildstein and Zalles (1995). Most obser-
vations began at 07h00 local time and usually ended at
17h00. Most raptors (>95%) were readily identified to
species using Porter et al. (1986), Clark (1999),
Jeyarajasingham and Pearson (1999),Wells (1999) and
Robson (2002). Weather conditions (wind speed,
barometric pressure, temperature, humidity) were
monitored hourly throughout the day with a hand-held
Kestrel 4000 ‘weather station’ (Nielsen-Kellerman
corporation, U.S.A.). Wind direction was determined
with a compass.
Observers scanned primarily north for approaching
migrants. An individual was considered a migrant if it
passed north-to-south across an imaginary east-west
50 ROBERT DECANDIDO et al.
Figure 2. Daily totals of raptors counted on migration at
Chumphon, Thailand, autumn 2003.
Ta ble 1. Raptor species, numbers counted, and seasonal peaks at Chumphon,Thailand, in autumn 2003.
O
SPREY Pandion haliaetus 31 (<1%) 5 Oct–9 Nov 18 Oct (6)
B
LACK BAZA Aviceda leuphotes 68,219 (40%) 21 Oct–9 Nov 23 Oct (42,046)
O
RIENTAL HONEY-BUZZARD Per nis ptilorhyncus 15,972 (9%) 10 Sep– 9 Nov 1 Oct (3,021)
B
LACK KITE Milvus migrans 124 (<1%) 27 Sep–9 Nov 10 Oct (29)
E
ASTERN MARSH HARRIER Circus aeruginosus spilonotus 178 (<1%) 27 Sep–9 Nov 23 Oct (25)
P
IED HARRIER Circus melanoleucos 11 (<1%) 27 Sep–2 Nov
C
HINESE SPARROWHAWK Accipiter soloensis 57,667 (34%) 27 Sep–9 Nov 11 Oct (10,389)
J
APANESE SPARROWHAWK Accipiter gularis 5,811 (3%) 9 Sep–9 Nov 23 Oct (606)
G
REY-FACED BUZZARD Butastur indicus 14,962 (9%) 14 Oct–9 Nov 23 Oct (9,985)
C
OMMON BUZZARD Buteo buteo 10 (<1%) 8 Oct–9 Nov
G
REATER SPOTTED EAGLE Aquila clanga 3 (<1%) 18 Oct–23 Oct
B
OOTED EAGLE Hieraaetus fasciatus 8 (<1%) 10 Oct–5 Nov
C
OMMON KESTREL Falco tinnunculus 4 (<1%) 18 Oct–23 Oct
E
URASIAN HOBBY Falco subbuteo 3 (<1%) 15 Oct–24 Oct
P
EREGRINE FALCON Falco peregrinus 8 (<1%) 8 Oct–18 Oct
U
NIDENTIFIED HARRIER Circus spp. 66 (<1%)
U
NIDENTIFIED ACCIPITER Accipiter spp. 1,168 (1%)
U
NIDENTIFIED BUZZARD Buteo spp. 5 (<1%)
U
NIDENTIFIED FALCON Falco spp. 4 (<1%)
U
NIDENTIFIED RAPTORS 6,411 (4%)
Total 170,665 23 Oct (56,101)
Species Number counted Dates seen Seasonal peak
(% of total migrants) (highest count)
line at the watch site, and continued south out of sight.
No attempt was made to determine the relative
proportion of males versus females, or of adults versus
immatures.Totals for large flocks (>300 individuals) of
Black Baza Avecida leuphotes, Chinese Sparrowhawk
Accipiter soloensis and Grey-faced Buzzard Bustatur
indicus were estimated to the nearest 25 individuals.
RESULTS
In total, 170,665 raptors of 15 species were counted
migrating during 378 hours of observation (averaging
452 birds/hour;Table 1). Black Baza was the common-
est migrant (68,219 individuals), representing 40% of
the 163,020 individuals identified to species (Table 1).
The largest flock of this species, estimated at 1,300
birds, passed on 23 October. Chinese Sparrowhawk
(57,667 individuals) made up 34% of all individuals
identified, with 550 individuals in one flock on 11
October. We also observed large numbers of Grey-
faced Buzzard (14,962 individuals; 9%; largest flock =
500 individuals on 23 October) and Oriental Honey-
Buzzard Pernis ptilorhyncus (15,972 individuals; 9%;
largest flock = 91 individuals on 7 October).
The highest single day count was 56,101 individu-
als of ten species on 23 October (Fig. 2). A peak of 11
species was observed on 18 October.There were differ-
ences between species in their seasonal pattern of
migration (Fig. 3). Of the five commonest species,
Chinese Sparrowhawk and Oriental Honey-buzzard
migrated through the area primarily before mid-
October, Grey-faced Buzzard and Black Baza migrated
primarily in late October, and Japanese Sparrowhawk
Accipiter gularis migrated through the area throughout
the autumn (Fig. 3).
Raptors at Chumphon typically migrated through-
out the day, sometimes from shortly after 07h00 until
shortly before 18h00 (Fig. 4). On most days,
movements of Chinese Sparrowhawk and Grey-faced
Buzzard peaked at 09h00–10h00. Oriental Honey-
Buzzard migration peaked at 10h00–11h00. About half
of all raptors (53%) were seen from 09h00 to12h00
(Fig. 4). On most days, counts decreased thereafter
until 15h00–16h00, when they again increased. Most
of the migrants (72%) were seen when cloud cover
exceeded 70%. Between 12h00 and 15h30, raptors
frequently flew at heights above 600–800 m, especially
if winds were <8km/hour. Entire flocks of certain
species (Chinese Sparrowhawk, Grey-faced Buzzard),
and individuals of other species (Oriental Honey-
buzzard, Japanese Sparrowhawk) sometimes
disappeared into the bases of clouds when they soared
in thermals. At 19h25 on 1 October 2003, CN
observed a flock of about 50 Chinese Sparrowhawks
entering a night-time roost in a coconut Cocos nucifera
grove near the watch site. Several species, including
Black Baza, Chinese Sparrowhawk, and Japanese
Forktail 20 (2004) 51Autumn 2003 raptor migration at Chumphon, Thailand
Figure 3. Number of (a) Black Baza, (b) Oriental Honey-
buzzard, (c) Chinese Sparrowhawk, (d) Japanese
Sparrowhawk and (e) Grey-faced Buzzard counted at
Chumphon, Thailand, in autumn 2003.
Forktail 20 (2004)
Sparrowhawk roosted in coastal mangrove forests
10–15 km north of the site.
We considered four species (Black Baza, Oriental
Honey-buzzard, Chinese Sparrowhawk and Grey-
faced Buzzard) to be obligate flocking migrants at the
site (sensu Kerlinger 1989). We also observed mixed-
species flocks of Grey-faced Buzzard and Black Baza,
and of Japanese and Chinese Sparrowhawk.
Individuals of several other species (e.g. Osprey
Pandion haliaetus, Black Kite Milvus migrans and
Greater Spotted Eagle Aquila clanga) were sometimes
seen in groups of two or more individuals. Several
researchers (Ash 1993, Wells 1999, Nijman 2001b,
Robson 2002) have noted flocks of Japanese
Sparrowhawk in South-East Asia, but we did not see
single-species flocks of this species at Chumphon.
More raptors were counted at the site on winds
from the west or north-north-west than the east or
south (P² = 41.7, P<0.05). From 27 September to 25
October, winds were typically light to moderate for the
entire day. Later in the season, early morning westerly
or variable winds shifted to on-shore, easterly winds by
about 10h00. Raptors were then seen primarily flying
north-to-south-west of the site, and after noon few
raptors were observed passing over the site itself.
Three additional raptor species (Black-shouldered
Kite Elanus caeruleus, Brahminy Kite Haliastur indus,
and White-bellied Sea Eagle Haliaeetus leucogaster)
were resident in and around Chumphon and were not
counted. Non-raptors seen migrating, or apparently
migrating, at the watch site included Little Cormorant
Phalacrocorax niger, Grey Heron Ardea cinerea, Purple
Heron Ardea purpurea,Oriental Pratincole Glareola
maldivarum, Grey-headed Lapwing Vanellus cinereus,
Pale-capped Pigeon Columba punicea, House Swift
Apus affinis, Asian Palm Swift Cypsiurus balasiensis,
Fork-tailed Swift Apus pacificus, Blue-throated Bee-
eater Merops viridis,Blue-tailed Bee-eater Merops
philippinus, Barn Swallow Hirundo rustica, Red-rumped
Swallow Hirundo daurica, Sand Martin Riparia riparia,
Ashy Minivet Pericrocotus divaricatus and Black Drongo
Dicrurus macrocercus (see DeCandido et al.2004).
DISCUSSION
Our counts demonstrate a significant autumn
movement of soaring raptors at Chumphon, Thailand.
The number of raptor species observed (15), the
number of individuals counted (170,665), and the
average number of raptors counted per hour (452) are
the highest totals reported to date in South-East Asia.
The numbers of five species (Black Baza, Oriental
Honey-buzzard, Eastern Marsh Harrier, Chinese
Sparrowhawk, and Grey-faced Buzzard) appear to be
among the highest single-season totals reported in Asia
(Medway and Nisbet 1964, Lin and Lin 1986,
Severinghaus 1991, Ash 1993, Kugai 1996, Chong
2000, Nitani 2000, Williams 2000, Nijman 2001b,
Tordoff 2002; see Table 2). Based on our observations,
we estimate that as many as 500,000 raptors may
migrate south over Chumphon each year between
52 ROBERT DECANDIDO et al.
Ta ble 2. Maximum autumn counts of raptors at sites in East Asia for the six most common migrants seen in autumn 2003 at Chumphon, Thailand. (See
Fig. 1 for locations).
B
LACK BAZA Avecida leuphotes 68,219 2003 Chumphon, Thailand This study
O
RIENTAL HONEY-BUZZARD Per nis ptilorhyncus 121,000 1963 Selangor Plain, Malaysia Medway and Nisbet (1964),Wells (1999)
E
ASTERN MARSH HARRIER Circus aeruginosus spilonotus 576 1986 Beidaihe, China Williams (2000)
C
HINESE SPARROWHAWK Accipiter soloensis 439,276 1999 Uchiyama-toge, Nagasaki, Japan Nitani (2000), Chong (2000)
J
APANESE SPARROWHAWK Accipiter gularis 7,835 1984 Bali Barat, Indonesia Ash (1993)
GREY-FACED BUZZARD Butastur indicus 31,784* 1999 Kohyamacho, Kagoshima, Japan Nitani (2000), Chong (2000)
*Unpublished data indicate that a higher count was made at the Miyako islands (Ryukyus), Okinawa, Japan: 53,575 individuals in autumn 1980; data from
1973–2003 give an annual mean of 27,859 individuals (Y. Nitani in litt. 2004).
Species Max. Year Location Source
count
Figure 4.Pattern of raptor migration through the day (birds/hour) at Chumphon,Thailand, in autumn 2003.
August and early December.This makes Chumphon a
watch site of global significance (Yosef et al. 2000,
Zalles and Bildstein 2000).
Small numbers of two other raptors (nine Steppe
Eagles Aquila nipalensis and two Imperial Eagles Aquila
heliaca) were seen migrating in early November at a
location c.8 km west of the site (not included in
Table 1). Further research may determine if several
other raptor species that are regarded as migrants in
Thailand (Hen Harrier Circus cyaneus,Western Marsh
Harrier C. aeruginosus aeruginosus, Shikra Accipiter
badius and Eurasian Sparrowhawk A. nisus) also
regularly pass through the area.
The raptors counted at Chumphon are thought to
follow at least two migration routes in East Asia: (a) an
Eastern Inland Corridor that extends from south-
eastern Siberia through eastern China and Indochina
(Laos, northern Vietnam, northern Thailand), south
through the Thai-Malay Peninsula; and (b) a Coastal
Pacific Corridor that extends from north-eastern
Siberia, Amurland, and Ussuriland through coastal
China, south into Indochina and the Thai-Malay
Peninsula (McClure 1998, Zalles and Bildstein 2000).
Movements along these corridors are poorly under-
stood, and additional study is needed to determine the
routes used by different raptors in the Far East (Ellis et
al. 1990, Lane and Parish 1991, Severinghaus 1991,
Ash 1993, Chong 2000, Nitani 2000, Williams 2000,
Nijman 2001a,Tordoff 2002). Satellite-tracking of two
Oriental Honey-buzzards in autumn 2003 showed that
they left their breeding grounds in Japan in mid-
September, crossed to mainland China and headed
south-west across Indochina, then south through the
Thai-Malay Peninsula to Sumatra (H. Higuchi in litt.
2004). Further studies may reveal the extent to which
outbound raptors including Oriental Honey-buzzard,
Chinese Sparrowhawk and Grey-faced Buzzard, follow
the Oceanic Pacific Corridor, before heading west to
the mainland, and south into Malaysia and Indonesia.
Weather conditions had a major influence on the
number of raptors migrating. Significantly more
raptors were seen when winds were from the north-
west quadrant than when winds were from the
south-east quadrant. Raptors seemed to ‘drift’ to the
coast with westerly winds when skies were overcast and
when strong thermals were lacking. With moderate
westerly winds, as many as 10% of the migrants passed
approximately 2 km to the east of the site along the
Gulf of Thailand. On 23 October, we counted 56,101
migrants during overcast skies and light to moderate
west to north-west winds. On that day the area <7 km
north and west of the watch site was free of precipita-
tion, but it was raining throughout much of central and
northern Thailand. Although steady rain at the watch
site ended raptor migration there, we believe that local
rains simply diverted migrants around the precipitation
cell. Observers in the Neotropics have also noted
migration in light or intermittent rain and overcast
skies (Bildstein and Saborio 2000).
Recommendations
The raptor migration at Chumphon affords an excep-
tional opportunity for research and education. We
recommend a season-long autumn count by experi-
enced observers from mid-August to late November, as
well as exploratory partial season spring counts in mid-
March through mid-May. Several (3–4) observers
would be needed in order to reduce observer fatigue.
Training of local people to assist with counts is needed.
Consideration should be given to a coordinated
transect count in the region, including searching for
large overnight roosts. There is no comprehensive
guide to flight identification of raptors for this part of
the world, and we suggest that printed and on-line
guides to the different raptors of East Asia be devel-
oped as quickly as possible. A poster depicting raptor
diversity in Thailand and South-East Asia could serve
as a keystone visual aid providing information about
Asian raptors. A children’s colouring book of the
common birds of Thailand with basic information
about urban and suburban raptors would create
interest at the grassroots level.
ACKNOWLEDGEMENTS
We sincerely appreciate the encouragement and thoughtful advice of
Phil Round of Mahidol University. Uthai Treesucon of Bangkok
provided many helpful ideas and suggestions to the raptor watch
team. We thank Hiroyoshi Higuchi of the University of Tokyo for
sharing some unpublished information. Yasunori Nitani of the Asia
Raptor Research and Conservation Organization (ARRCN)
provided migration count data for Chinese Sparrowhawks and Grey-
faced Buzzards in Japan. Anne Arrowsmith designed the map. We
deeply appreciate the kindness shown to us by our colleagues of the
Malaysian Nature Society including Laurence and Audrey Poh,
Cheang Kum Seng, Liew Siew Lan and Ooi Beng Yean, Regina
Anthony and Chiu Sein Chong as well as Lim Aun Tiah and Lim
Kim Chye. Desmond Allen provided GPS coordinates of the site.
David Wells read a version of this manuscript and provided helpful
comments. Those wishing to observe raptor migration at Chumphon
should contact Chukiat Nualsri (bntern@chaiyo.com) for details
about how to reach the watch site, and the annual Raptor Watch
festival usually held in the second week of October. Our research was
supported by grants from the Bobolink Foundation and the Oriental
Bird Club, and by a Hawk Mountain Sanctuary Project Soar Award.
This is Hawk Mountain Sanctuary Contribution to Conservation
Science number 108.
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54 ROBERT DECANDIDO et al.
Robert DeCandido, Acopian Center for Conservation Learning, Hawk Mountain Sanctuary, 410 Summer Valley Road,
Orwigsburg, Pennsylvania 17961 U.S.A. Correspondence: 1831 Fowler Avenue,The Bronx, New York 10462-3708.
Email: rdcny@earthlink.net
Chukiat Nualsri,Thayang Administrative Organization, 135-1 Kromluang Chumphon Road, Muang Chumphon
86000,Thailand. Email: bntern@chaiyo.com
Deborah Allen,The Linnaean Society of New York, P.O. Box 1452 Peter Stuyvesant Station, New York 10009, U.S.A.
Email: dallenyc@earthlink.net
Keith L. Bildstein, Acopian Center for Conservation Learning, Hawk Mountain Sanctuary, 410 Summer Valley Road,
Orwigsburg, Pennsylvania 17961 U.S.A. Email: Bildstein@hawkmtn.org