Vol
14 No 1
Water
Regime Management
Bird Ringing 2006
Shorebird counts (2000-2006)
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Shorebird
Counts (2000-2006)
at Sungei Buloh Wetland Reserve
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By James Gan
Senior Conservation Officer
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Main
article | Peak High Tide Counts part
1, part 2 |
Comparison of selected species | Day
Peak Counts
 Summary
Shorebirds from the Scolopacidae and Charadriidae were counted regularly
in Sungei Buloh Wetland Reserve between January 2000 and December
2006. A total of 23 species was recorded during the census sessions.
Total shorebird numbers peaked in October, November or December for
all years. The most abundant bird was the Pacific Golden Plover Pluvialis
fulva with counts consistently exceeding 1,000 for all years since
2001 with a maximum of 2,000.
The counts have revealed information on the composition of shorebird
species, their numbers and their presence in different months over
the past seven years. More specifically, the relative importance of
Sungei Buloh as a shorebird site in Singapore is reinforced. Data
collected will help to improve the conservation work and management
practices at Sungei Buloh for the next few years.
Introduction
This article is based on an earlier paper submitted by the same authors
and published in The Stilt No.48 Oct 2005. It is an update of the
shorebird count data obtained from monthly wader census conducted
at SBWR with a brief analysis. It is also the intention of this update
to prime people to take a greater interest and appreciation in the
shorebirds of Singapore.
Results
A total of 23 species was recorded during the census sessions. Seven
of the 23 species dominated with counts of at least 100 birds at any
one session during the study period. Count data for these seven species
for the period January 2000 to December 2006 are listed in Table 1.
Note that the totals as given in the tables refer to the highest count
for a given month and are not average counts.
For all years, maximum shorebird counts were in either November or
December with the exception of 2006 when it peaked in October. Peak
counts of shorebirds did not exceed 3,200 birds in any year. Only
the Pacific Golden Plover had counts exceeding 1,000 birds. This occurred
fairly regularly during both the periods for southward and northward
migration. The only other shorebird with numbers exceeding a thousand
was the Mongolian Plover Charadrius mongolus (1,003 on January 2000).
Common Redshank Tringa totanus and Whimbrel Numenius phaeopus were
the only two species noted in the boreal summer for 2001 to 2006 where
they were present in very low numbers (below 20 birds) except in June
2003 when no shorebirds were observed.
To generalise, the species with the highest numbers recorded during
the southward migration (Sep/Oct/Nov) relative to their numbers throughout
the year were Common Redshank, Mongolian Plover and Curlew Sandpiper.
Species with the highest numbers recorded during the northward migration
(Mar/Apr) were Pacific Golden Plover and Whimbrel. Species with the
highest numbers in the northern mid winter (Dec/Jan) were Common Greenshank
and Marsh Sandpiper.
Species Account
A comparison was made of the seven most common shorebird species at
the reserve with the maximum counts recorded by the Asian Waterfowl
Census (AWC) for Singapore between 1991 and 2001 (Perennou & Mundkur
1991, 1992; Mundkur & Taylor 1993; Lopez & Mundkur 1997; Li & Mundkur
2004). Direct comparison is possible for counts taken in January since
the AWC counts are consistently conducted in that month at low tide.
The percentage of each species of shorebird that can be found in the
reserve against the Singapore population is at best a rough estimate
but still an indicator of the relative importance of the reserve with
respect to other sites in Singapore. The relevant data are given in
Table 2.
 Common
Greenshank
Tringa nebularia
Trend: Increased numbers during both southward and northward migration
The maximum count at the wetland was 364 recorded in Nov 2005. It
seems likely that during high tide about half the population of Greenshanks
in Singapore use the wetland as a roost.
 Common
Redshank
Tringa totanus
Trend: Increased numbers during both southward and northward migration
The maximum count was 683 recorded in Sep 2000. The peaks in September
followed by a 60% to 70% drop the following month in 2000, 2001 and
2002 provide some indication of turnover rates for Redshanks on passage.
 Curlew
Sandpiper
Calidris ferruginea
Trend: Erratic numbers during the southward migration. Avoidance
of the wetland during the northward migration since the spring of
2001 The maximum count was 519 in Oct 2006. The 1991-2001 counts for
Singapore range from 5 to 781. First migrants were recorded in August.
Since 2001, negligible (less than 10) numbers of birds were present
between January and July. The data and observation could be explained
by the possibility that since 2001, Curlew Sandpipers take a northward
migration route that bypass or use other wetlands in Singapore or
the region. Such an alternative route could possibly be along the
eastern coast of Sumatra before crossing over to Malaysia and/or Thailand.
Large numbers of Curlew Sandpiper occur along the east coast of Sumatra
at this time (A. Crossland pers. comm.). Wader counts at suitable
sites in Indonesia and the Malay Peninsula would help to clarify the
actual route taken. The peak counts in October for most years indicate
a strong southward passage in that month before falling sharply in
January for the northward migration.
 Marsh
Sandpiper
Tringa stagnatilis
Trend: Stable numbers during both southward and northward migration.
The maximum count was 486 observed in Dec 2001. Counts for Singapore
range from 526 and 1294. Birds arrive at the wetland in appreciable
numbers only from October. The data collected are consistent with
the observations in the Malay Peninsula where Marsh Sandpipers arrive
late and depart relatively early with a further peak in the boreal
spring (Wells 1999). This surge was noted in early April 2001 but
not in 2000. It may however have happened between count dates and
was therefore unrecorded.
 Mongolian
Plover
Charadrius mongolus
Trend: Steady recovery in numbers during the southward migration
after a dramatic and steep decrease observed in 2002 and 2003; Avoidance
of the wetland during the northward migration since the spring of
2003. The maximum count of 1,003 was recorded on 26 January 2000.
Another count of 878 was recorded on 10 February 2000. AWC counts
for Singapore have recorded historic peaks of up to 1,000 birds. Observations
in the Malay Peninsula have generally noted decreases in Mongolian
Plover numbers from December to March (Wells 1999). These observations
are consistent with the pattern of counts recorded for all years when
counts are generally highest in December and decrease as the northward
migration progresses. This may indicate a boreal spring exodus without
significant augmentation by passage migrants. High tide counts taken
from a boat in the West Johore Straits on 3 Jan 03 revealed up to
600 Mongolian Plovers resting on floating pontoons. The following
year, on 6 Feb 04, 200 Mongolian Plovers were counted at the same
pontoons during high tide. Thus it would seem, unlike the Curlew Sandpiper,
that the main northward migration route of Mongolian Plovers continues
to include the vicinity of Sungei Buloh. Further monitoring and implementation
of various habitat management measures at Sungei Buloh may help to
reveal the reasons for the general avoidance of the wetland in favour
of the pontoons during the northward migration period.
 Pacific
Golden Plover
Pluvialis fulva
Trend: General increase in numbers during both the periods of
southward and northward migration. Counts exceeded 1,000 birds in
all years except 2000. A mid-winter peak count of 2000 was recorded
in Jan 2005 and this number is unusual as Jan counts for Pacific Golden
Plovers in previous years had never exceeded 1,000 birds. It could
however indicate some disturbance at the Mandai Mudflats where records
of Pacific Golden Plovers exceeding 2,000 birds at low tide have been
recorded. The southward migration in the same year confirmed this
number with a peak of 1,735 birds counted in Nov 2005. The following
year also saw an unusually high surge of Pacific Golden Plovers in
Jan 2006 with a count of 1,321 birds. AWC counts for Singapore range
from 908 to 2416. There appears to be a trend that more Pacific Golden
Plovers are making use of Sungei Buloh. The reasons are not clear
but could be due to the loss of previously derelict land in the Kranji
area that had been used by the plovers as a high tide roost area and
which was in 2005 and 2006 being redeveloped resulting in the plovers
moving to Sungei Buloh as the next best high tide roost. The count
of 1,081 birds in April 2001 suggests staging during northward migration.
 Whimbrel
Numenius phaeopus
Trend: Increased numbers during both southward and northward migration
A maximum count of 442 was obtained. That count was taken in Nov 2003
and likely involves birds passing through and making use of Sungei
Buloh as a stop over site. Significant increases in Whimbrels from
the preceding months in April 2001 (219 birds), Mar 2002 (215 birds),
Mar 2004 (301 birds), Apr 2005 (320 birds) and Apr 2006 (268 birds)
might indicate staging. The high counts of Whimbrels in Mar and April
quickly slumps to generally 20 birds or less in early May. Some Whimbrels
may have over summered in Singapore as small numbers were present
throughout May, June and July in most years. First arrivals were noted
in late July or early August and a large influx of birds was noted
in September for most years.
DISCUSSION
This study of shorebird count data from the years 2000 to 2006 has
shown that generally, for counts between September and March (Table
3), over 1,000 shorebirds may be expected at SBWR during the high
tide period. From May to July, only a few species of shorebirds can
be found, usually Common Redshank and Whimbrel with fewer than 30
individuals. From the census data for the seven years period, the
shorebird community at the reserve is composed of seven main species
and sixteen other species that occur in much smaller numbers. These
in descending order of abundance are Common Sandpiper Tringa hypoleucos,
Terek Sandpiper Tringa cinerea, Broadbilled Sandpiper Limicola falcinellus,
Ruddy Turnstone Arenaria interpres, Bar-tailed Godwit Limosa lapponica,
Little Ringed Plover Charadrius dubius, Great Knot Calidris tenuirostris,
Pintail Snipe Gallinago sterura, Eurasian Curlew Numenius arquata,
Grey-tailed Tattler Tringa brevipes, Grey Plover Pluvialis squatarola,
Red-necked Stint Calidris ruficollis, and Black-tailed Godwit Limosa
limosa, Little Curlew Numenius minutes, Greater Sand Plover Charadrius
leschenaultii and Asian Dowitcher Limnodromus semipalmatus. Other
shorebird species, for example Black-winged Stilt Himantopus himantopus
observed at the reserve in 2005 (Tay 2006) were not recorded during
the actual census sessions.
Preliminary data obtained through the counts and observations suggest
that the wetland is favoured by perhaps more than 80% of the Singapore
population of Whimbrel, Mongolian Plover (except during the northward
migration period when they completely avoid the wetland) and Pacific
Golden Plover. The data also suggest that about 50% of the Common
Greenshank and 30% of the Marsh Sandpiper and Common Redshank population
use the wetland as a high tide roost. About 10% of the Curlew Sandpiper
population is thought to use Sungei Buloh as a high tide roost. Further
studies would be required to confirm these hypotheses. More frequent
counts over a longer period would help to establish patterns of seasonal
abundance, distribution and movements of shorebirds in Singapore.
A limitation of the data obtained during the study period is that
a substantial influx of passage waders might last only a few days
and might be missed through slipping between counts that are spaced
at wider intervals. Closer-spaced counts during migration periods
would refine our knowledge of the exact magnitude and timing of passage
peaks. The data presented, though limited by resource constraints,
is however sufficient to give an indicative picture of the seasonal
abundance of shorebirds at Sungei Buloh. It is clear that the Sungei
Buloh wetland area is an important site for these shorebirds. Similar
sites in Singapore and around Singapore may possibly reveal similar
species, similar monthly counts and composition of species.
Acknowledgements
The counts were possible through the assistance of the Conservation
Officers and Rangers at Sungei Buloh Wetland Reserve. In particular
we would like to register our appreciation to Abdul Khalid Hamid,
Mustaffa Hajar, Charles Lim Sim Moh, Patricia Phua Lee Kheng, Lim
Yew Soon, Jack Wong and the late Ong Hai Chwee for logistical assistance.
References
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Buloh Wetland Reserve in 2001, Wetlands Vol 9, No. 1, Pp13. Publication
of SBWR, National Parks Board, Singapore
Gan, J. and Ramakrishnan, R.K. 2005. Notes on shorebird numbers in
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Press, San Diego |
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wetlands