NAT. NAT. HIST. BULL. SIAM SO C. 31 (2) : 151-155 ，198 3.

NOTES

An Uoidenti :fi ed Large in the Gulf of T hailand

Between 1100-1200 hours 00 17 December 1977 ， the authors found a large gull 0 ( (Larus sp.) perched on the end of the picr at Bang Pu ，Samut Prakan Province (1 3 29 'N ， I00046'E). I00046'E). Observations were made at ranges down to 10 m using 8x 30 binoculars. Photographs Photographs were also taken and notes on the 's appe a rance were tape-recorded at the the time. The bird was significantly larger than the Brown-headed Gull L. brunnicephalus and Bl ack-headed GuII L. ridibundus ，which were available for direct comparison. J. B.， who is very familiar with both the Herring GuII L. argentatus and the Lesser Black-backed Black-backed Gu Il L. fuscus in Europe ， noted that the bird was at least the same size as as these two (similarly-sized) and was possibly slightly larger. The general colouration colouration was brown and white and the detailed plumage description indicates a bircl in in first winter plumage. The entire bill was dark brown ancl the legs were ftesh - coloured. coloured. The biII was ， if anything ，les s hea vy than that of L. a . argentatus known to

J.B. J.B. Th 巴 forehead was white; the crown and nape were whitish ， ftecked with brown as was the breast. White edgings to the brown feathers gave a scalloped effect to the

man tI e and to alI wing feathers except the primaries ，which were uniformly v巴ry dark brown. brown. The rump was white ， graduating with brown spots to a broad ， dark brown subterminal subterminal tail band. The very tips of the retrices were narrowly edged with white (Figures (Figures 1-3). The Brown-headed GuII and the Black-headed Gu I1 are the only species li s ted for Thailand Thailand in LEKAGUL & CRO NIN (1 974). Of the larger guIIs that have so far been observed in in Southeast Asia (KI NG et a! ，1975) ， the Great Black-headed Gu Il L. ichthyaetus can can certainly be ruled out as is it usuaIIy obviously larger than a Herring Gull and the immature has a prominent scaly pattern on the mantle and scapulars ，a prominent brownish brownish lower hind neck and brownish breast patches (G RANT ， 1982). Th y Bang Pll bird bird was therefore on the sides to the breast most likely to have been either a Herring Gull Gull or a Slaty-backed Gull L. schistisagus ，immatllres of which may not be separable with with certainty in the field (SO N OBE & ROBINSO N ，1982). Although both species breed in nOfth-e a. st Asia ， there are only a few records of the Slaty-backed GuII from the E as t

1 51 152 J. BOSWA LL AND S.KANWAN ICH

China Sea (SH UNTO V，19 7 4) and fi ve records from Hong Kong (W EBSTE R， 1975). The Herring Herring Gull winters commonly along the coast of China as well as along the Chang

Jiang Jiang and Xi Jiang rivers (CHE NG， 1976) and is the second ・most numerous gull in Hong Kong ， after the Black-headed (D.S. ME LV ILLE ，in litt.) . The re a re also a few records from Vietnam (D ELA COUR & JABO UILLE ， 1931; Vo Q UY，197 5). On the basis of their known distributions ，therefore ， the Bang PU bird is mo st li kely ι to have been a Herring Gul l. However ，first year Herring GuIIs from the W este rn Pal ea rctic typically show pale inner primaries primaries and barred outer greater coverts (GR ANT ，1 982 and in litt.) ，which the Bang

PU bird lacked. lf ， as se ems likely ， this disti nct ive ch aracter is sh ar巴d by first year Herring Herring GuIIs of the eastern races such as L. a. taimyrensis ，L. ' a・vegae and L. a. mongolicus ， then it would strongly suggest that the B ang PU bird was either the Slaty- backed GuII or possibly even Lesser Bl ack-backed Gul l. Both these species apparently share share all dark primaries ， lacking an y obvious pale a rea on the inner primaries ， with the greater greater coverts forming a solid drab band ，less ob viou sly mottled and pale-edged than in in the Herring Gu Il (D W IGHT ，1925 ; G RANT，1982) . The Lesser Bl ack-backed Gull is perhaps less li k ely to occur in Th a iland than Slaty-backed ， although it has been reported from the western shore of the Bay of Bengal Bengal (Au & RIPLE Y， 1970). KI NG (1 983) has record ed two first winter ， either L. L. argentatus or L. fuscu s，on Lake lnle ，Burma ，and has further commented that in lndia lndia L. argentatus norma lI y winters on inl and bodi 巴s of w a ter whereas L. fuscus tends to to stay in coastal areas. To summarise ， the plum ag e chara ct ers of the large gull seen at Bang PU suggest that that it was most likely to have been either a Slaty-backe d Gull or a Lesser Black-backecl Gull. Gull. However ，on the basis of probability of occurre nc e， Herring Gull would seem to be a more likely candidate and this species cannot be excluded from consideration without without further elllcidation of the plumage ch aracters of immature of its eastern Palearctic Palearctic races . None of these three sp ec ies h as been pr ev iollsl y recorded in Thailan d. Careful Careful documentation of all sllbsequent OCCllrr ences of th e large r gulls in Thailand is necessary necessary if their identification is to be r esolved. Grateful Grateful acknowledgem e nt is made to Ben Kin g， Peter Grant ，David Melville and PhH Round . NOTES 153

Figure Figure 1 (top). Unidentifi ed 1arge gu lI in flight ，Ban Bang PU Kao ， 17 De cember 1977 . Figure Figure 2 (middle) . Unidentified 1a rge gu Il (on right) ，and two immature Brown-headed GuIIs GuIIs L. brunnic e phalus (note : one bruunicephalus is immediate1y behind the 1arger 1arger gu Il) . Figure Figure 3 (bottom) . Unid entified 1a rge guII (on right) and three Brown-headed Gu Il s for comparison when perched . ~-...，...ー『目ヤ予守苧 NO TES 155

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ALI ， S. and D. RIPLEY. 1970. Handbook 01 the Birds ollndia and Pakistan. O.U .P.

CHENG ，Tso ・hsin .1 976. Distributiona/ /i st 01 Chinese birds. Science Press ， Peking. DELACOUR ，J . and P. JABOUILL E，193 1. Les Oiseaux de 1'lndochine Francaise. Vo l. 1. Exposition Coloniale Coloniale International ，Paris . DWIGHT ， J. 1925. Gulls of the World. Bull. Amer. Mus. Nat. Hist. 52: 63-336. GRANT ，P.J . 1982 . Gu l/ s，A Guide to ldentz 冗calion. Poyser ， Calton.

K ING ，B . 1983 . N 巴w bird distribution data for Burma. Nat . Hisl. Bu l/. Siam Soc . 31 (1) : 55 - 62. KING ，B. ，M . WOODCOCK and E.C. DICKI NSON. 1975. A Fie/d Guide /0 /he Birds 01 South-easl Asia. Asia. Co Jl ins ，London. LEK AGUL ， B. and E.W. CRONIN . 1974. Bird Guide to Thai/and 2nd ed. Association for the Conservation Conservation of Wildlife ，Bangkok. SHUNTOV ， V.P. 1974. Sea birds and the biologica/ structure 01 the ocean (translation). U.S. Department of Commerce ，Springfield ，Virginia. SO NOBE ，K. and J.B. ROBI NSON (eds.). 1982. バ Field Guid e 10 th e Birds 01 Japan. Wi ld Bird Society Society of Japan ，Tokyo VO QUY. 1975. Chim Vietnam ，vo l. l. Hanoi. WEBSTER ，M .A. 1975. . An Annota/ed Ch ec k /i st 01 Ihe Birds 01 Hong Kong ，3 rd ed. Bird Watching Society ，Hong Kong.

Jejf rey Bo s wall Birdswell ，Wraxall Bristol Bristol BS19 lJ Z England Sup r α(lit Kallwfwic !z Association for the Conservation of Wildlife 4 Old Custom House Lane New Road ，Bangkok 10500