Comparison of Spring Migration Phenology of Bee-eaters and Oriental
Honey-buzzards Pernis Ptilorhynchus at Tanjung Tuan, Malaysia,
By Robert DeCandido, Deborah Allen, Reuven Yosef & K. L. Bildstein
This article was originally published in the Ardea 92(2),
2004 and was kindly submitted by Robert DeCandido.
DeCandido R., D Allen, R. Yosef & K. Bildstein 2004. A comparison
of spring migration phenology of bee-eaters and Oriental Honey-buzzards
Pernis ptilorhyncus at Tanjung Tuan, Malaysia, 2000-01. Ardea
92(2): 169- 174
Counts of migrating Blue-tailed Bee-eaters Merops philippinus
and Bluethroated Bee-eaters M. viridis, as well as five raptor
species were made in March 2000 and March 2001 at Tanjung Tuan, a
coastal migration watchsite in western Malaysia. Totals of 2226 bee-eaters
(12.9 bee-eaters h-1) and 11 441 raptors (66.5 raptors h-1) were counted.
The Blue-tailed Bee-eater comprised 60.8% of Merops individuals
(1353 birds) that could be identified. The Blue-throated Bee-eater
was much less common, comprising 10.0% of the flight (222 counted).
Oriental Honey-buzzards Pernis ptilorhyncus comprised 93.1%
(10 648 individuals) of the raptor flight. Bee-eater and Honey-buzzard
migration peaked during 11:00-16:00h, and both generally preferred
westerly winds to make landfall at Tanjung Tuan.
Key Words: Merops philippinus - M. viridi - Pernis
ptilorhyncus -migration - Malaysia - East Asian Flyway
Since the 1950s, Oriental Honey-buzzards Pernis ptilorhyncus
have been known to migrate northeast from Sumatra across the Straits
of Malacca to the west coast of Malaysia each spring (Oakeley 1955;
White 1961; Medway & Nisbet 1965; Medway & Wells 1976; Wells
1990). Recently it was discovered that significant numbers of Bluetailed
Bee-eaters Merops philippinus and Bluethroated Bee-eaters
M. viridis also use the same route each year (Medway &
Wells 1976; Fry et al. 1992; Wells 1999). However, information regarding
routes, timing and destinations of diurnal migrants on this East Asian
Flyway in both spring and fall are not well known (see McClure 1974;
McClure 1998; DeCandido et al. 2004). In Southeast Asia, migrating
bee-eaters and Honey-buzzards travel in flocks, interspersing flappingflight
with soaring in thermals whenever possible. In this paper we analyze
the diurnal rhythm of migrating bee-eaters and Honey-buzzards where
both make landfall on the Asian mainland after an overwater crossing
of at least 38 km.
Port Dickson (2°24’N, 101°51’E, sea-level) is
a small town on the west coast of Malaysia situated on the Straits
of Malacca, approximately 94 km southwest from Kuala Lumpur (Fig.
1-2). It is located at the southern end of a south to north range
of mountains that presumably funnels spring migrants north along the
western lowlands of the Malay Peninsula (Medway & Nisbet 1965;
Wells 1999). The watchsite, known locally as Tanjung Tuan, is situated
on the deck of a lighthouse, south of Port Dickson at km 16, approximately
3 km west of the coastal highway. The lighthouse, built by the Dutch
in the 18th century, sits atop a rocky peninsula providing a 180-
degree view to the west, south and north; it is surrounded by coastal
evergreen rainforest in a small, forest reserve. On clear days it
is possible to see Sumatra approximately 38 km across the Straits
of Malacca to the southwest. This is the shortest overwater distance
along the Straits from Tanjung Medang on the island of Pulau Rupat
of northwestern Sumatra (Zalles & Bildstein 2000).
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
(7); Miyako Islands (Ryukyus), Okinawa, Japan (8); and Bali
Barat National Park, Indonesia (9). See DeCandido et al.
(2004) for information about these watch sites.
Migrants were counted during 8-22 March 2000 (104 observation h) and
2-12 March 2001 (68 h) by DA and RDC using 8.5x and 10x binoculars.
Observations typically began at 09:00-10:00 h local time and usually
ended by 17:00 h. DeCandido identified, counted, and recorded the
numbers of bee-eaters and raptors seen, while Allen photographed the
migration. Most bee-eaters (75.9%) and almost all raptors (> 99%)
were identified to species level. Weather conditions typically were
hazy-cloudy with little windin the morning till 10:00 h, then becoming
clear but humid. On many days at approximately 10:45 h, a 3-12 km
h-1 sea breeze from the west/northwest would begin. On certain days
the wind direction and speed changed significantly in subsequent hours.
Wind direction was measured by recording the reading shown on the
weather vane mounted atop the lighthouse and a handheld compass.
We scanned mainly to the west across the Straits of Malacca in the
direction of Sumatra from the patio of the lighthouse. Bee-eaters
and raptors were considered migrants if they passed west-to-east across
an imaginary north-south line and continued west and out of sight
past the lighthouse and nearby hills. Occasionally, migrants did not
pass the immediate area of the watchsite but continued on a northeastern
course over the Straits of Malacca, presumably making landfall north
of the lighthouse towards Port Dickson. We pooled the number counted
of both Merops species along with all bee-eaters we could
not identify to species level.
In 2000-01, a total of 2226 bee-eaters of two species (12.9 birds
h-1) were counted during 26 observation days. These included 1353
Bluetailed Bee-eaters (60.8%), 222 Blue-throated Bee-eaters (10.0%)
and 651 unidentified individuals (29.2%). Also, a total of 11 442
raptors (66.5 birds h-1), were counted in migration. Oriental Honey-buzzard
was the most common raptor, making up 93% (10 648 total; 61.9 birds
h-1) of the flight in 2000-01. Black Bazas Aviceda leuphotes
comprised 5.3% (608 total), and Chinese Goshawk Accipiter soloensis
(62), Greyfaced Buzzard Butastur indicus (48) and Japanese
Sparrowhawk A. gularis (12), accounted for 1.1% (4.6 birds
h-1); 64 raptors could not be identified. The majority of bee-eaters
(84.0%) were seen from 11:00-16:00 h (Fig. 3). The highest hourly
total occurred between 13:00-14:00 h on 21 March 2000 when 101 Blue-tailed
Bee-eaters were counted. Once the first flock of bee-eaters arrived
at the Cape, scattered flocks would follow for 4-6 h each day on most
days, especially after 10 March. Exceptionally, bee-eater migration
would last for seven (17 March 2000) to eight (21 March 2000) consecutive
hours on a given day. On peak flight days, the arrival of bee-eaters
began in the 09:00-10:00 h (17, 20 and 21 March 2000). Flocks were
not usually seen after 16:00 h, and no bee-eaters were recorded migrating
after 17:00 h. High daily counts of bee-eaters occurred after 15 March
2000, frequently when winds with a westerly component were moderate
to strong (> 15 km h-1) as on 16 March 2000 (169 counted), 17 March
2000 (254) and 19 March 2000 (248). Overall, 30.1% of the bee-eater
flight in 2000-01 was counted on these three days of moderate to strong
winds. However, the highest day counts in both years occurred on days
with light (< 10 km h-1) winds: 11 March 2000 (139 counted) and
21 March 2001 (326).
Most (95.0%) migrating Oriental Honey-buzzards were seen from 11:00-16:00
h, with a decided peak between 11:00-12:00 h, and a second, smaller,
peak between 14:00-15:00 h and small flocks up until 18:30 h only
on days of high counts (2 and 12 March 2001). The highest hourly count
in 2000-01 was 841 individuals from 11:00- 12:00 h on 9 March 2001.
The majority (96.7%) of Honey-buzzards made landfall at the Cape with
light to moderate (< 15 km h-1 and usually < 10 km h-1) winds.
Generally, light winds with a westerly component produced the best
Oriental Honey-buzzard flights. However, in 2001, of the four days
with > 1000 Honey-buzzards counted, three had light winds from
the NE to E, and the fourth had light northwestern winds.
: Number of bee-eaters and Oriental Honey-buzzards counted
in migration by hour of the day at Tanjung Tuan, Malaysia, in March
Since the 1950s in Malaysia there has been known a significant migration
of raptors that are returning each spring from Sumatra to the Asian
mainland in the area of Tanjung Tuan. However, only a few published
accounts provided information about the daily and seasonal raptor
migration phenology at the site (Oakeley 1955; White 1961; Medway
and Nisbet 1965; Wells 1990; 1999). Even fewer data exist for the
number of individuals of the two Merops species that utilize
this same route each spring (see Medway & Wells 1976; Wells 1999).
In Southeast Asia, the handful of bee-eater migration reports present
data from single days of observation (see David-Beaulieu 1944; David-Beaulieu
1949-50; Melville and Fletcher 1982; Tizard 1996; Evans 2001). The
only long-term study of migrating bee-eaters comes from Hong Kong
(Carey et al. 2001). Even there, data are based upon a small
sample: a maximum 30-year aggregate of 30-40 individuals total, counted
by week in spring.
At Tanjung Tuan, Oriental Honey-buzzards and bee-eaters showed a diurnal
migration pattern typical of soaring birds (Kerlinger 1989), with
a late morning peak, an indication of a noon lull and steeply declining
passage in the late afternoon. Both species (groups) use thermal soaring
and active flight during migration, and readily cross large bodies
of open water. In the closely related European Honey-buzzard Pernis
apivorus and European Bee-eater Merops apiaster flying
speeds were very similar between both species groups (Bruderer &
Boldt 2001), but Honey-buzzards showed a wide variation in gliding
and flapgliding speeds depending on environmental conditions (Bruderer
et al. 1994). The – on average – earlier arrival of bee-eaters
at Tanjung Tuan may have been caused by employment of active flight
to a greater degree, a lesser dependence on thermals than broad-winged
raptors and/or taking advantage of favourable weather conditions in
Sumatra (thermals) and Malaysia (onset of seabreeze from the W and
NW at about 10:45 h) earlier than Honey-buzzards. Both bee-eaters
and Honey-buzzards declined rapidly as migrants after 15:00 h, but
why only Honey-buzzards were seen in migration after 17:00 h remains
to be determined.
Bee-eaters were more likely then Oriental Honey-buzzards to make landfall
at Tanjung Tuan when winds were moderate to strong (> 15 km h-1)
from the NW-W (DeCandido et al. 2004). Several high daily
bee-eater counts occurred on moderate to strong wind days, when simultaneously
no Oriental Honey-buzzards were counted in migration. All Honey-buzzard
flights at the Cape were correlated with light winds (< 15 km h-1,
usually < 10 km h-1). It seems likely that varying numbers of bee-eaters
and Honey-buzzards are migrating in all wind speeds and wind directions
along a fairly broad front as they approach Tanjung Tuan. Moderate
to strong westerly winds concentrated the bee-eater flight at the
Cape probably because it was the closest site to make landfall. What
factor( s) influence Honey-buzzards to choose Tanjung Tuan to make
landfall in large numbers on certain days but not others remain to
be determined. Light winds, sometimes with a westerly component, produced
the best Honey-buzzard flights, but on other days with the same conditions,
few Honey-buzzards appeared. Also, large flights of Honey-buzzards
occurred on days with NE-E winds. The influence of wind direction
and speed upon migrants at Tanjung Tuan warrants additional investigation,
as do the factors that initiate movements of particularly large numbers
of bee-eaters and raptors. In any event, conditions in Sumatra probably
play the most important role in determining the extent and timing
of bee-eater and Honey-buzzard migration at the Cape on any given
We thank two anonymous reviewers, and especially Rob Bijlsma, for
erudite comments and suggestions that greatly improved this manuscript.
Anne Arrowsmith designed the two maps. We sincerely appreciate the
encouragement and thoughtful advice given by members of the Malaysian
Nature Society including Laurence and Audrey Poh, Liew Siew Lan and
Ooi Beng Yean, Regina Anthony and Chiu Sein Chiong, Cheang Kum Seng,
Lim Kim Chye and Lim Aun Tiah. David Melville and Jevgeni Shergalin,
the latter of the Hawk Mountain Sanctuary Acopian Center for Conservation
Learning, provided the authors with important reference material regarding
Southeast Asian Merops migration. Dr. William Duckworth of the Wildlife
Conservation Society suggested many helpful ideas, as well making
us aware of the historical information regarding Merops spp. in Indochina.
This is publication number 123 of the Hawk Mountain Sanctuary. We
dedicate this paper to the memory of Laurence Poh, 1952-2004.
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Robert DeCandido, Hawk Mountain Sanctuary, Acopian Center for
Conservation Learning, 410 Summer Valley Road, Orwigsburg, Pennsylvania
17961, USA Email: email@example.com
Deborah Allen, P.O. Box 1452 Peter Stuyvesant Station, New York 10009
U.S.A. Email: firstname.lastname@example.org
Reuven Yosef, International Bird Research Center, P.O. Box 774, 88106
Eilat, Israel. E-mail: email@example.com
Keith L. Bildstein, The Linnaean Society of New York, P.O. Box 1452
Peter Stuyvesant Station, New York, New York 10009 USA. Email: firstname.lastname@example.org