migration of Oriental Honey-buzzards Pernis ptilorhyncus
and other raptors at Tanjung Tuan, Malaysia, 2000–2001
By Robert DeCandido, Deborah Allen and Keith L. Bildstein
This article was originally published in Forktail 22 (2006) the journal
of the Oriental
Bird Club (OBC) and was kindly submitted by Robert
Please support the OBC's conservation
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Since the 1950s, it has been known that wintering populations of Oriental
Honey-buzzards Pernis ptilorhyncus and at least four other
raptor species migrate each spring from Sumatra north-east across
the Straits of Malacca to the west coast of Malaysia (Oakeley 1955,
White 1961, Medway and Nisbet 1964, 1965, Medway and Wells 1976, Wells
1990a, 1990b). This migration is part of the East Asian Flyway, with
most birds presumably returning to breed in the region from western
China and southern Siberia east to Japan (McClure 1998, Zalles and
Bildstein 2000, DeCandido et al. 2004a,b, Higuchi et al. 2005). However,
the magnitude, timing and duration of the migration of Oriental Honey-buzzard
and other species using this route remain unclear (Wells 1999, Zalles
and Bildstein 2000). Here we report results from counts made in March
2000 and 2001.
Port Dickson (2°24'N 101°51'E, 0 m) is a small town on the
west coast of Malaysia on the Straits of Malacca. It is c.94 km south-west
of Kuala Lumpur and 90 km north of the city of Melaka (Figs. 1–2).
The town is located at the southern end of a range of mountains that
runs northsouth and presumably funnels many migrants along the western
coastal lowlands of the Malay Peninsula (Medway and Nisbet 1965, Wells
1999). The watch site is situated on the deck of a lighthouse, south
of Port Dickson at km 16, c.3 km west of the coastal highway, and
is known locally as Tanjung Tuan. The lighthouse is surrounded by
coastal evergreen rainforest in a small, protected forest reserve.
On clear days it is possible to see Sumatra c.38 km across the Straits
of Malacca to the south-west. From Tanjung Medang on the island of
Pulau Rupat of north-western Sumatra to Tanjung Tuan is the shortest
distance over the sea along the length of the Straits of Malacca (Zalles
and Bildstein 2000). Weather conditions typically were hazy or cloudy
with little wind in the morning until 10h00, then becoming clear but
humid. On many days a 3–15 km/h sea breeze from the west or
north-west developed at c.10h45. Occasionally, the wind direction
and speed changed significantly in subsequent hours.
1 : Location of Tanjung Tuan in relation to Sumatra.
2 : Location of Tanjung Tuan, Malaysia (1) relative
to other important raptor migration watch sites in East Asia:
Selangor Plains, Malaysia (2); Chumphon, Thailand (3); SaPa,
Vietnam (4); Beidaihe, China (5); Uchiyama-toge, Nagasaki, Japan
(6); Kohyamacho, Kagoshima, Japan (7); Miyako Islands (Ryukyus),
Okinawa, Japan (8); Kenting National Park, Taiwan (9); and Bali
Barat National Park, Indonesia (10). See DeCandido et al. (2004b)
for further details.
Migrating raptors were counted during early to mid-March in 2000 and
2001 by RDC and DA using 8.5× and 10× binoculars. In 2000,
104 hours of observations were made on 15 days (8–22 March).
In 2001, observations were made for 68 hourson 11 days (2–12
March). Observations typically began at 09h00–10h00 andusually
ended by 17h00. On nine occasions in 2000, and four occasions in 2001,
we left the count site at 15h00 because fewer than 25 migrant raptors
had been counted after 12h00. RDC identified, counted, and recorded
the numbers and species of raptors seen, while DA assisted, acting
primarily as a spotter while photographing the migration (see Porter
et al. 1986, Inskipp et al. 1996, Clark 1999, Jeyarajasingham and
Pearson 1999). Over 99% of raptors were readily identified to species.
Both observers scanned mainly to the west across the Straits of Malacca
in the direction of Sumatra. An individual raptor was considered to
be a migrant if we observed it pass west–east across an imaginary
north–south line, and continued east and out of sight past the
lighthouse and nearby hills. We defined a flock of migrating raptors
as any group of at least two individuals making landfall within 100
m and five minutes of one another. Wind direction was measured using
a weathervane mounted atop the lighthouse and a handheld compass.
Ambient wind speed was estimated from experience: it could not be
measured directly at the watch site because the configuration of the
lighthouse blocked or deflected wind currents on the lighthouse deck.
To examine the diurnal timing of Oriental Honey-buzzard migration,
we included data from counts taken in 1998 (45.5 hours during 2–8
March) and 1999 (35 hours during 1–5 March 1999) by Lim Aun
Tiah of the Malaysian Nature Society (MNS). We used Chi² tests
to examine the significance of variation in arrival times.
In total, 11,442 migrating raptors were counted in 2000– 2001
(an average rate of 66.5 birds/hour). In 2000, we counted 3,188 migrant
raptors (30.7 birds/hour): 2,519 Oriental Honey-buzzards, 561 Black
Bazas Aviceda leuphotes, 30 Chinese Goshawks Accipiter
soloensis, 18 Greyfaced Buzzards Butastur indicus and
five Japanese Sparrowhawks Accipiter gularis, plus 55 unidentified
individuals. In 2001, we counted 8,254 migrant raptors (121 birds/hour):
8,129 Oriental Honey-buzzards, 47 Black Bazas, 32 Chinese Goshawks,
30 Grey-faced Buzzards and seven Japanese Sparrowhawks, plus nine
unidentified individuals. Additional migrating raptors, almost all
likely to have been Oriental Honey-buzzards, were seen by other observers
making landfall along the Malaysian coast north and south of the watch
site during our study, but these are not included in our totals.
Oriental Honey-buzzard was the most common migrant, making up 93%
of migrating raptors in 2000–2001, followed by Black Baza (5.3%),
with Chinese Goshawk, Grey-faced Buzzard and Japanese Sparrowhawk
comprising the remainder. We recorded five other raptor species that
we assumed to be resident: Black-shouldered Kite Elanus caeruleus,
Brahminy Kite Haliastur indus, White-bellied Sea Eagle Haliaeetus
leucogaster, Changeable Hawk Eagle Spizaetus cirrhatus
and Black-thighed Falconet Microhierax fringillarius.
In 1998–2001, Oriental Honey-buzzards were significantly more
likely to be seen during 11h00–13h00 than at other times of
day (59% of records, (Chi²=3751.4,d.f.=1, P=0.001, Fig. 3). Like
Wells (1999), we found that the Oriental Honey-buzzard migration was
usually concentrated into a 4–5 hour period after the arrival
of the first wave of migrants, and few individuals were seen after
this time. On the eight days in 2000–2001 on which we counted
more than 100 Oriental Honey-buzzards per day, the first arrivals
were at 11h08 on average (standard deviation=35.9 min).
The majority of Oriental Honey-buzzards (96.7%) made landfall during
light to moderate (<15 km/h) winds. When winds exceeded 20 km/h,
we did not observe any migrating raptors making landfall. Over 99%
of Oriental Honey-buzzards were recorded in flocks (184 flocks in
total), and just 14 individuals were recorded migrating alone. Mean
flock size was 57.7 individuals, and the maximum was 388 individuals.
The highest single hour total of Oriental Honey-buzzards was 841 at
11h00–12h00 on 9 March 2001.
The maximum daily count of Black Bazas was 325 individuals (in one
flock) on 17 March 2000. The period in which migrants were recorded
was 2 March–22 March for Oriental Honey-buzzard, 9 March–21
March for Black Baza, 2 March–21 March for Chinese Goshawk,
2–21 March for Japanese Sparrowhawk and 2–17 March for
Most (>75%) Oriental Honey-buzzards and all individuals of the
other four species were observed migrating eastwards within 300 m
of the watch site. All migrants arrived from below eye-level to a
maximum height of 30 m. Oriental Honey-buzzards were often first seen
low in flapping flight over the sea as they attempted to gain altitude
about 500 m from shore. Black Baza and Chinese Goshawk were only observed
arriving in gliding flight in flocks at a height of c.30 m.
3 : Diurnal pattern of Oriental Honey-buzzard Pernis
ptilorhyncus migration at Tanjung Tuan, Malaysia, during 1998–2001.
Figure 4 : Frequency distribution of migrant Oriental
Honey-buzzard Pernis ptilorhyncus flocks at Tanjung Tuan,
Malaysia in 2000–2001.
Our observations confirm previous records of significant numbers of
migrant raptors at Tanjung Tuan, e.g. L. A. Tiah (in litt. 2002) counted
5,093 migrating Oriental Honey-buzzards (112 birds/hour) in early
March 1998, and 1,040 (63.7 birds/hour) in early March 1999. Our maximum
hourly totals also accord with previous records: 680 individuals/hour
on 3 March 1964 (Medway and Nisbet 1965), 670 on 2 March 1998 and
616 on 4 March 1998 (L. A. Tiah in litt. 2002).
We observed the largest daily numbers of Oriental Honey-buzzards in
early March. Since 1955, daily totals of Oriental Honey Buzzards at
Tanjung Tuan exceeded 1,000 individuals on: 1 March 1987 (2,761: J.
M. Thiollay quoted in Wells 1999), 2 March 1998 (1,516: L. A. Tiah
in litt. 2002), 2 March 2001 (1,758: this study), 3 March 2001 (1,285:
this study), 4 March 1983 (1,552: see Wells 1990a), 4 March 1998 (1,115:
L. A. Tiah in litt. 2002), 6 March 2001 (1,222: this study), 15 March
2000 (1,136: this study), 26 March 1964 (1,200: see Medway and Nisbet
1965) and 27 March 1964 (1,602: see Medway and Nisbet 1965). The first
Oriental Honey-buzzard migrants of the season have been seen as early
as late January (Medway and Wells 1976) to 13 February (Oakeley 1955),
and as late as 2 April (White 1961, Wells 1990a), and 3 April further
south over Singapore (Hurrell 1961).
Other authors have recorded earlier and later dates of migrant raptors
than those we recorded, reflecting the limited duration of our visits.
Wells (1999) noted the earliest Chinese Goshawks around Tanjung Tuan
on 3 February, and the latest on 15 April, while C. Nualsri (in litt.
2005) recorded 84% of individuals of this species at Chumphon, Thailand,
during 28–30 March 2005. Wells (1999) recorded Japanese Sparrowhawk
at Tanjung Tuan from 15 February to early May, with peak passage on
21 March–15 April. For Black Baza, 96% of migrants were seen
during 16–30 March at Chumphon, Thailand (C. Nualsri in litt.
2005). For Grey-faced Buzzard, the earliest migrants at Hulu Klang
(Selangor) near Kuala Lumpur were on 17 February 2006 (M. Chong in
litt. 2006), while migration peaked in early to mid-March at Chumphon,
with 79% of individuals during 8–19 March in 2005 (C. Nualsri
in litt. 2005).
Five additional raptor species have been recorded migrating at the
site: Osprey Pandion haliaetus, Blackshouldered Kite, Black
Kite Milvus migrans, Eastern Marsh Harrier Circus (aeruginosus)
spilonotus and Common Buzzard Buteo buteo (Wells 1990a,
1999, Zalles and Bildstein 2000). Non-raptor migrants (including Bluetailed
Bee-eater Merops philippinus and Blue-throated Beeeaters
M. viridis) have been described elsewhere (DeCandido et al.
Our findings with regard to wind direction and wind speed in relation
to raptor migration generally agree with Wells (1990a, 1999). Usually,
raptors made landfall nearest the lighthouse when winds were light
and had a westerly component. When westerly winds exceeded 10 km/h,
greater numbers of migrating raptors were sometimes counted 6 km south
at Kampung Segenting (L. A. Tiah in litt. 2002). When winds were north-easterly,
raptors tended to drift further north up the coast. However in early
March, light winds from other directions occasionally produced significant
numbers of migrating honey-buzzards: during 14h00–15h00 on 2
March 2001, we counted 809 Oriental Honey-buzzards on east–northeast
winds of 2–10 km/h. The following day with similar winds, we
counted 377 honey-buzzards during 11h00–12h00, with much of
the migration passing to the north. When winds switched to south–south-east
by 13h00, we counted 801 honey-buzzards, mostly passing to the south.
Our observations of the diurnal timing of raptor migration, which
showed a clear peak at 11h00–13h00 (Fig. 3), closely agree with
those of Wells (1990a). Possible explanations for this peak include:
(a) the location of appropriate roosting areas in north-eastern Sumatra;
(b) the timing of the onset of thermals in coastal Sumatra; and (c)
the timing of changes in meteorological conditions, especially wind
direction and speed, at Tanjung Tuan. All of these warrant additional
investigation, as do the factors that initiate movements of particularly
large numbers Oriental Honey-buzzards. Compared to Agostini et al.
(2005), who found that 82% of Eurasian Honey-buzzard Pernis apivorus
flocks crossed the Tyrrhenian Sea from Cape Bon (Tunisia) to mainland
Italy during 12h00–15h00, we found that the majority of Oriental
Honeybuzzard flocks (52%) made landfall from 11h00–13h00. The
difference was probably because the European birds had to make a much
longer (>150 km) sea crossing.
The total numbers of migrant raptors each year at Tanjung Tuan is
still not known, because observations have only been for only relatively
brief periods of time per season (single day counts in the 1950s,
three days in 1964, six days in 1983, and 15 days in 2000 and 11 days
in2001). On 3–6 March 2001, MNS members formed a north–south
team of observers (an ‘interception line’) stationed along
the coast stretching from 6 km south of the Tanjung Tuan at Kampung
Segenting to the northern part of Port Dickson town. They found that
28% (of 4,302) migrating Oriental Honey-buzzards made landfall north
and south of Tanjung Tuan. Based on these data, the totals we counted,
and the limited duration of our observations in the two seasons, we
estimate that 10,000–20,000 Oriental Honey-buzzards make the
crossing from Sumatra to the west coast of Malaysia each spring. By
comparison, Medway and Wells (1976) estimated that c.180,000 Oriental
Honey-buzzards migrated south over west peninsular Malaysia in autumn
1963. Recent observations in spring at Tanjung Tuan suggest daily
maxima of 1,500–1,800 individuals are likely at Tanjung Tuan,
with both historical and recent counts indicating that the peak of
the Oriental Honey-buzzard migration is likely to be in early March.
Overall, the number of Oriental Honey-buzzards counted at Tanjung
Tuan are similar to spring counts of migrating Eurasian Honey-buzzards
making long (>15 km) sea crossings at Italy and Gibraltar (Giordano
1991, Agostini 1992, Zalles and Bildstein 2000), and recent autumn
migration counts of Oriental Honey-buzzards in Thailand (DeCandido
et al. 2004b).
We recommend the following: (1) a season-long count from mid-February
to mid-May should be conducted by experienced observer(s) in order
to determine the magnitude of the migration of all raptor species;
(2) in early March, a north–south ‘interception line’
of observers perpendicular to the line of migration should be set
up from several kilometres north of the lighthouse in Port Dickson
to several kilometres south of the lighthouse in order to validate
the percentage of migrants that are not observed from Tanjung Tuan;
(3) a ringing programme should be established to determine the condition,
age and sex of individuals arriving through the season; (4) a watch
site should be set up in a highly accessible location (e.g. the grounds
of a hotel) near Tanjung Tuan, coinciding with demonstrations involving
captive birds of prey. Most people in Malaysia are unaware of the
great diversity of migrant species that pass through their country
in spring and autumn. Using the spectacle of raptor migration at Tanjung
Tuan combined with live, captive birds of prey affords a significant
opportunity to make many influential people aware of this annual phenomenon
in the area of Port Dickson.
We dedicate this research to the late Laurence Poh and his wife, Audrey.
We greatly appreciate the encouragement and thoughtful advice of members
of the Malaysian Nature Society including Ooi Beng Yean and Liew Siew
Lan, Chiu Sein Chiong and Regina Anthony, Cheang Kum Seng, Dr. Chan
Kai Soon, Mike Chong, Lim Aun Tiah and Lim Kim Chye. Chukiat Nualsri
provided information regarding spring migrating raptors near Chumphon,
Thailand. Anne Arrowsmith designed the maps. David Wells provided
many helpful comments and ideas. William Duckworth critically read
the manuscript and directed us to historical information about bird
migration in South-East Asia. We wish to acknowledge the hospitality
shown to us by members of the Tanjung Tuan lighthouse staff. This
is Hawk Mountain Sanctuary Contribution to Conservation Science number
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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 U.S.A. Email: firstname.lastname@example.org
Deborah Allen, P.O. Box 1452 Peter Stuyvesant Station, New York 10009
U.S.A. Email: email@example.com
Keith L. Bildstein, Acopian Center for Conservation Learning, Hawk
Mountain Sanctuary, 410 Summer Valley Road, Orwigsburg, Pennsylvania
17961 U.S.A. Email: firstname.lastname@example.org