THE DISTRIBUTION OF MIGRATORY WADERS IN SOUTH-WEST SARAWAK Phillip J. Edwards & Duncan Parish Edwards,P.J. & Parish,D. 198•. The distribution of migratory waders in south-west Sarawak. Wader Study Group Bull. 54: 36-40. The first complete survey of waders to be undertaken on the south-west coast of Sarawak was carried out between Santubong and Kuaia Igan during the period of southward migration in 1985. Combining the results of a ground and an aerial survey gives a minimum usage for this stretch of coast of 30 757 waders plus 357 at two inland sites. Thirty-four species of wader were observed including two new records for Sarawak. The distribution of waders was found to be heavily in•iuenced by the presence of healthy mangrove systems. One site of international importance was discovered - Putau Bruit. This held almost 604 o• all the waders recorded during the survey including over 14 of the world populations of Asian DowitcherLimnodromus semipaimatus and Eastern Curlew Wumenius madagascariensis. Phillip J. Edwards, Environmental Management Consultants Ltd., The Old School, Carlton, Newmarket, Suffolk CB8 9JY, UK. Duncan Parish, Asian Wetland Bureau, Institute of Advanced Studies, Universiti Malaya, Lembah Pantai, 59100 Kuaia Lumpur, Maiaysia. INTRODUCTION METHODS Of all the wetlands of the world, least is Before undertaking the field surveys, known about those of South-east Asia while topographic and land-use maps of the entire concurrently there is perhaps most human Sarawak coastline were examined together with pressure upon them. In addition to their oblique colour aerial photographs taken as part commercial value, these coastal wetlands are of the National Coastal Erosion Survey (Stanley important to large numbers of waders migrating Consultants 1985). These enabled easy between their Dreeding grounds in northern identification of areas with extensive China and Russia and their non-breeding grounds mangroves and mudflats, those with sandy in Australia. In order to elucidate the routes substrate, and those sections which are these waders use, their major refuelling stops, eroding. These studies indicated that the only and the numbers involved, the East Asia/Pacific areas with wide mudfiats were in the two large Shorebird Study Programme (INTERWADER) was bays at either end of the state. The bay established in 1983. As part of its 1985 immediately east of Kuching was selected for programme, a survey of the major mangrove and the first survey (Figure 1) and a later study mudflat areas of the Sarawak coast was looked at Brunei Bay (Howes and NPWO 1986b). undertaken. Ground surveys were undertaken using 10 x 40 Utilization of coastal areas by migrant waders binoculars and 20 x 60 telescopes mounted on in $arawak has previously been little studied. tripods. Beaches and mudflats were surveyed Limited observations were made by Smythies either from small fishing boats or, more (1957), Fogden (1965, 1966), Croxall (1969), satisfactorily, after landing from small speed and Burton (1978) and some collections were boats. In the case of sand or hard mud, the made by Banks (1935) and Harrison (1950, 1957). area could be traversed easily on foot. 'Where However, no comprehensive survey was completed. extensive areas of soft mud were encountered, This paper provides details of the first landing was possible only from the numerous complete survey of waders to be undertaken on rivers that bisected the flats, and counts were the south-west coast of Sarawak, carried out made, therefore, only from these places. between Santubong and Kuaia Igan from 28 Surveys were made for the most part by two September to i November 1985 and of an aerial people, one identifying and counting, the other survey conducted on 8 November 1985. recording. Checks were made at random intervals by reversing the roles. In cases where only one person was able to survey, counts were made STUDY AREA AND HABITATS into a pocket tape-recorder and transcribed later in the day. Sarawak, one of the two East Malaysfan states, is situated on the northern side of the island All stages of the tidal cycle were encountered of Borneo. The coastline is approximately 1 050 during the survey period. By consulting km long and is orientated generally in a SW-NE tide-tables it was attempted to survey sandy direction. Much of this length comprises sandy coasts near high tide in order to identify beaches but two areas of extensive mangrove and high-tide roosts. Muddy coasts were counted mudflats occur in a large bay east of Kuching near mid-tide, where possible, and preferably in the south-west of the state, and in Brunei on the flood so that boats did not get Bay in the north-east. The majority of the stranded. Time allowed only one count along sandy coast is vegetated with Casurina each part of the coast with the exception of equestifolia and backed by ribbon development Jerijeh North Sands (counted at both high and of agriculture. The mangrove areas are low tide on the same day) and a small section dominated by Rhizophora spp. and, where the of Pulau Bruit (counted twice, 3 weeks apart). coast is actively accreting, by Avicennia marina. The palm Nipa fruticans predominates Aerial surveys were made using helicopters along the banks of the estuarine rivers. provided by the RMAF. One was flown between 37 RESULTS ',• Mudflats x•, Limits of iurv©y A total of 28 694 waders were recorded during the ground survey while the subsequent aerial suzvey produced a count of almost 23 000. The difference between these totals may be accounted for by difficulties in counting birds from the air, e.g. high speed and in places high altitude, leading to under-estimation. Differences may also be due to the onward migration of some birds between the ground surveys in September and October and the aerial survey in November. Not all the aerial counts were, however, lower than the corresponding ground ones. In some sectors, where the ground counts were hampered by poor access or bad weather, the aerial counts revealed larger concentrations of waders. The figures have been combined, therefore, to give a maximum count. This reveals 30 757 waders on this part of the coastline with another 357 found on the two inland sites (Table 1). Of the 28 694 waders observed during the ground survey, 20 576 (71.74) were identified to genus or species. Thirty-four species were recognised of which two were new records for Sarawak, namely Black-winged (or Pied) Stilt Himantopus himantopus ieucocephalus and Sharp-tailed Figure 1. hocation of the survey area. Sandpiper Caiidris acuminata (Edwards and Polshek 1987). Table 2 provides a breakdown of the numbers recorded by species and by survey sector. It shows that the five most abundant Kuching and Samunsan (to the west) at 1 000 ft species were Redshank Tringa totanus (18.44) , and at 1 000 ft in a Sikorsky 61. No waders Greater Sandplover Charadrius leschenauiti were recorded, possibly because the altitude (15.34), Terek Sandpiper Xenus cinereus was too great. The aerial survey coinciding (13.64), Red-necked Stint Caiidris ruœicollis with most of the area covered on the ground was (8.04;, and Curlew Sandpiper Calidris flown in an Allouette Mk .3 at 60-i00 knots œerruginae (7.74). below 5U0 ft. Count data were recorded on tape together with information on habitat. Coastal Sites Photographs were taken at important sites. Figure 2 illustrates the distribution of waders over the 14 coastal sectors surveyed. No particular pattern emerges from this although Table I. Distribution of waders by sector along the Sarawak coast, recorded during ground and aerial surveys in September - November 1985. Ground Aerial max•%r:.• • MaX. Sector Survey Survey Coun• Count S. Buntai - S. Bako 1 161 270 1 161 3.73 West coast •ako NP 149 NS 149 0 48 East coast Bako NP 98 211 211• 0 68 M Tebas - K. Samarahan 34 46 46 •' 0 15 K Samara•an - K. Sadong 4 054P 5 3?2 5 372 17 27 K Sadong - K. Lupar 154 151 i54 0 5O K Lupar - K. Saribas 622 473 622 2 00 K Saribas - K. Kabong 1 263 145 1 263 4 06 K Kabong - K. Rajang 600 913 913 2 94 K Rajang - K. Beiawai 746 94 746 2 4O K Beiawai - K. Paloh 368P 940 940 Pulau Bruit 18 597 14 300 18 597 59 77 Pulau Patok 256 NS 256 0.82 Maura Lassa - K. Ig•n 317 NS 317 1.02 Sub-total 28 331 22 943 30 757 98.•1 Tekajong marsh and rice paddies 134 NS 134 0.43 Kuching Airport 223 NS 223 0.75 TOTAL 28 688 22 943 31 114 NS = Not surveyed, P = Partial count, S = Sungai, K = Kuala, M = Muara The maximum count column contains the number of birds recorded on either the ground or aerial surveys - whichever is the highest. The 4 maximum count is the percentage of birds recorded in each sector, based on totals in the maximum count column. Table 2. Distribution of different wader species by sector along the Sarawak coast. A B C D E F G H I • K L M N o P TOTAL % Bhck-winged Stilt 3 3 0.01 Oriental Pratincole 109 0.38 Grey-headedLapwing 1 0.01 Pacific Golden Plover 34 157 0.55 Grey Plover 13 246 372 1.30 Little Ringed Plover 1 17 0.06 Kentish Plover 1• 3 55 0.19 MalaystanPlover 1 4 0.01 MongolianPlover sb 9 51 • 114• 1266 4.41 Greater Sandplover 3O3 41• 23 741 I91 179 49 I179 3137 10.93 Black-tailed Godwit 2 4 1 3 1074 I084 3.78 Bar-tailed Godwit 16 22 25 581 695 2.42 Limosa sp.