FO@9TA"+ -0 %-00(35 '0*E''> Over-ocean raptor migration in a monsoon regime: spring and autumn 2007 on Sangihe North Su!a"esi Indonesia FRANCESCO $ERMI, GEORGE !2 ?OUNG, AGUS SALIM, WESLEY ,ANGIMANGEN and MARK SCHELLEKENS Buring spring and autumn -00) we carried out full season raptor migration counts on !angihe "sland, "ndonesia2 "n autumn, -;0,-'* migratory raptors were recorded2 Chinese !parrowhaw6 Accipiter soloensis comprised appro8imately (8C of the flight2 The count results indicate that the largest movements of this species towards the wintering grounds of eastern "ndonesia occur along the East Asian Oceanic Flyway, and not the Continental Flyway as previously thought2 /oth spring and autumn migrations occurred in the face of monsoon headwinds2 The relationship between migrant counts and day to day variation in wind direction in !angihe differed between the two seasons2 &ore migrants were counted during crosswind conditions in spring when their route ta6es them along closely spaced islands than during similar conditions in autumn, when they run the ris6 of being blown off course during longer over water legs2 Bisplacement over the sea by crosswinds coupled with records from other islands point to the e8istence of an additional and heretofore un6nown eastern route, involving longer water crossings, between &indanao and the northern &oluccas via the Talaud "slands2 <e gathered evidence that Chinese !parrowhaw6 behave nomadically during the non breeding season, following local food abundances of seasonal insect outbrea6s induced by rains2 ,redictable landfall time on !angihe suggests that traditional roosts of thousands of migrants occur on small islands along this oceanic route2 Anmonitored land use conversion on these remote islands could result in the loss of vital roosting habitats2 INTRODUCTION The migration of raptors in the East Asian Continental and Oceanic Flyways has been sporadically investigated throughout this vast region, which stretches for more than 80 degrees of latitude from north east !iberia to eastern "ndonesia and #ew $uinea %&cClure '()*, +ane and ,arish '((', Chong -000, .alles and /ildstein -000, Chong and #itani -00', /ildstein and .alles -000, 1iguchi et al2 -00032 From the bre eding areas in the northern third of eastern Asia, the migratory flight splits into two ma4or corridors5 the East Asian Continental Flyway, a (,000 6m long, mostly overland route stretching from !iberia and China to mainland !outh East Asia and the "ndonesian Archipelago7 and the East Asian Oceanic Flyway, a ),000 6m island hopping route e8tending from north eastern !iberia, eastern China, 9orea and :apan to Taiwan, the ,hilippines and "ndonesia, involving water crossings of up to ;00 6m %Fig2 '32 <ith hundreds of thousands of raptors migrating along this route, the latter is the world=s ma4or oceanic raptor migration system2 1owever, despite a recent increase of regular watch sites across the region, substantial gaps remain in our 6nowledge of the spatial and temporal migration routes, the numbers of migrants on passage and their ecology in the largely undefined wintering grounds2 To date, the migration of raptors in the East Asian Flyways remains the least understood in the world %Ferguson +ees and Christie -00', /ildstein -00>32 Taiwan is the only country in the Oceanic Flyway where a long term monitoring programme has been implemented, providing a highly detailed account of raptor migration through the island and useful information to predict movements towards lesser studied neighbouring countries %+in and !everinghaus '((8, Chen C2!2C2 -000, -00>, -00), Chen C2!2C2 and !un -00), Chen ?2:2 -00>, #igure $2 &ap of the East Asian Oceanic and Continental Flyways2 Cheng et al2 -00>, !un -00>, @aptor @esearch $roup of /lac6 arrows show the autumn migration paths2 The study sites of Taiwan -00832 Other studies along the Oceanic Flyway !angihe and /ali are enclosed in sDuares2 For6tail -0 %-00(3 !pring and autumn -00) raptor migration on !angihe, "ndonesia '00 have been carried out in :apan %/raFil and 1anawa '((', main crop trees %@iley -00-, <hitten et al2 -00-32 The 9ugai '((>, #itani -000, in litt. -00), !hiu et al2 -00>3, average temperature is ->E-8GC with little seasonal whilst until now no structured counts have been variation7 the average rainfall is J;,000 mm per year, underta6en in the ,hilippines2 with a distinct wet season from #ovember to &arch %/,! "n "ndonesia, where nearly all Chinese !parrowhaw6s -00>32 Accipiter soloensis overwinter, raptor migration studies remain very much in their infancy, and the few wor6s of Surve( techni)ues relevance were all conducted along the Continental Of the chain of islands forming the suspected migration Flyway2 After Ash=s discovery of a migration route over corridor between &indanao and !ulawesi, we chose /ali in '(8- %Ash '(8*3, two studies were carried out as !angihe because of previous records of migrants and the partial season counts %Ash '((;, #i4man -00*3, but they logistical facilities available2 <e e8trapolated the passage provided only an incomplete and in instances erroneous periods in reviewing the scant published records from account of the autumn passage over Bali and Java (Nijman peer reviewed literature and birdwatching trip reports5 et al2 -00>32 !ubseDuently, several counts were carried all records of migrants from !angihe and ad4acent areas out across the country by a networ6 of "ndonesian #$Os, within "ndonesia, and count results from established birdwatching clubs and local universities during the -00'E regular watch sites in southern Taiwan, were collated in -00* period %!u6mantoro et al2 -00032 A more concerted order to predict the more li6ely passage dates on the island2 and intensive research initiative was underta6en in /ali in <e assumed that casual records of large migrating floc6s, -00*E-000, where more than (0,000 raptors were all from non migration related studies, possibly reflected observed on migration in autumn -000, yielding a periods of pea6 passage2 "nterviews with local villagers previously unrecognised dimension of raptor movements also provided a clue to the migration periods2 /efore throughout "ndonesia %$ermi -000, $ermi and <aluyo fieldwor6 started, one of us %F$3 visited the s6in collections -00>32 /ased on these findings, we hypothesised that at Tring &useum, A9, to study the age related plumages other ma4or corridors within the archipelago might have of Chinese !parrowhaw6 and :apanese !parrowhaw6 been overloo6ed, in particular from the Oceanic Flyway2 Accipiter gularis for field identification purposes2 An e8amination of autumn migration count results from &igration counts on !angihe were conducted during established watch sites in :apan and Taiwan suggested ' &archE'> April -00) %spring migration3 and -0 that the large numbers of southbound raptors were li6ely !eptemberE;0 #ovember -00) %autumn migration32 "n to winter not only in the ,hilippines, but also in eastern order to investigate wintering presences, additional "ndonesia and possibly #ew $uinea2 The geography of fieldwor6 was carried out between ' Becember -00) and the Oceanic Flyway indicates two li6ely entry corridors to ' &arch -0082 $eneral survey techniDues and migration "ndonesia5 %a3 from the ,hilippines into /orneo via count protocols adopted the guidelines summarised by ,alawan %!impson '(8;, Ellis et al2 '((0, Bavison '((), /ildstein and .alles %'((03 and /ird and /ildstein %-00)32 +im et al2 -00-3, and %b3 the volcanic arc of islands between Following a preliminary analysis of appropriate '500,000 &indanao %,hilippines3 and !ulawesi %"ndonesia3, the topographic maps and reconnaissance of the island by car so called !angihe and Talaud Archipelago2 The few and on foot, five strategically located watch sites were published records of migrating raptors from !angihe selected in spring, and an additional two in autumn %Fig2 Talaud and #orth !ulawesi %&eyer and <iglesworth -32 Four watch sites %#aha airfield, /ulong, 9ale6ube '8(8, <hite '()>, <hite and /ruce '(8>, @oFendaal and Bagho3 were at or near sea level, whilst the other and Be66er '(8(, @iley '((), 1ornbuc6le -00'3 three %,usunge, +enganeng and /owong /aru3 were on supported our hypothesis and suggested that a significant mountain ridges or hill tops and provided unrestricted but still unDuantified migration occurred along this views and close sight of the migrants7 nevertheless the corridor, hence prompting the underta6ing of this study2 latter three were often engulfed in low clouds, particularly during spring2 The watch site at ,usunge %0;K;)�0-”# '-0K;0�18”E, 08* m3 has a ;>0K view over the northern METHODS and central part of the island, and was used as the main watch site through the study2 Appro8imately )0E80C of Stud( area the possible flight front over the island was in view from !angihe island %0;G;0�# '-0G;-�E3 is part of the !angihe the watch sites of ,usunge and #aha7 however we and Talaud Archipelago, an arc of volcanic islands that gathered evidence that migration also occurred over the rises from a narrow submarine ridge e8tending from sea, at and beyond the limit of aided vision2 &oreover, !ulawesi to the ,hilippine island of &indanao2 This low cloud cover reducing visibility, especially during Hstepping stone= route involves water crossing distances &arch and early October %both pea6 migration periods3, of between ; and '(0 6m2 !angihe is *8 6m long and >E probably resulted in un6nown numbers of migrants '( 6m wide, with a surface area of );) 6mI and a rugged passing undetected2