Possible Winter Quarters of the Aleutian Tern?

Short Communications

Wilson Bull., 11 l(4), 1999, pp. 559-560

Norman F? Hill ’ and K. David Bishop* 3

ABSTRACT-Recent observations of the Aleutian (alternate) plumage in late August but most Tern (Sterna aleutica) in the coastal waters around then molted into non-breeding (basic) plum- Hong Kong in spring and fall, and Singapore and the age during September. Details of the latter, Indonesian islands of Karimun and Bintan between poorly known plumage, can be found in Lee October and April indicate that at least part of the population of this species migrates through and winters in (1992), Kennerley and coworkers (1993) and these areas. Our observations during December 1997, Kennerley and Ollington (1998). Subsequent- suggest that the coastal waters of Java, Bali and Su- ly, small numbers have been observed annu- lawesi may form an additional part of the winter range ally in Hong Kong waters including individ- of this species. Received 3 August 1998, accepted 17 uals in breeding plumage during April-June. June 1999. It is now established there as a regular and fairly common migrant in varying numbers. Several hundred migrants have also been re- The Aleutian Tern (Sterna aleutica) breeds corded annually in August and September, along the western coast of Alaska (USA) and with occasional birds recorded in October in Asia on the east coast of Kamchatka and (Leven et al. 1994; Carey et al. 1995, 1996). Sakhalin (American Ornithologists ’ Union From September to October 1994 this spe- 1998). In Alaska, birds return to colonies dur- cies was common within the Riau Archipela- ing early May and then disperse during Au- go, Indonesia, and a single bird was also re- gust and September after breeding, (Harrison corded there in March 1996 (Rajathurai 1996). 1983). Both the AOU Checklist (1998) and Kennerley and Ollington (1998) observed Harrison (1983) state that this species ’ winter small numbers between 18 September and 25 range is “unknown”. April in the Straits of Malacca and in the seas During the last decade or so there has been around the island of Grand Karimun with a a steady accumulation of records for this spe- maximum number of 15 positively identified cies outside its breeding range from Southeast birds on 19 January 1996, with more than 100 Asia. Lee (1992) reported six specimens col- distant terns also present. lected in May 1984 in the Mindanao Sea off Small numbers of Aleutian Terns were also Bohol, Philippines. Brazil (1991) noted ap- observed off the east coast of Singapore in proximately ten records from Honshu and September and October 1994 (Kennerley and Hokkaido, Japan including one instance of Ollington 1998). No records were reported probable breeding. One exceptional record in- during 1995 but a concerted effort to locate volves the occurrence of a single vagrant bird this species in 1996 resulted in at least 15 on the Fame Islands off the coast of northeast birds sighted 13 October in the Straits of Sin- England during May 1979 (Dixey et al. 1981). gapore between Jurong and the Horsburgh More recently, during August and September Light (Kennerley and Ollington 1998). 1992 as many as 190 birds were observed off We report here the first probable records tbe southern and southeastern coast of Hong from Java, Bali, and Sulawesi in the Republic Kong (Kennerley et al. 1993). of Indonesia and identify a likely proportion Initially birds were observed in breeding of this species ’ wintering range. On 30 November 1997 between Labuan I38 North Main Street, Assonet, MA 02702. and the north coast of Ujung Kulon National * Semioptera‘ ,’ F!O. Box 6068, Kincumber, NSW Park, at the western tip of Java, from a boat 225 1, Australia. 3 Corresponding author; E-mail: kdbishop@ozemail. we observed, about 20 probable adult Aleu- com.au tian Terns in groups of 3-6, all in non-breed-

559 560 THE WILSON BULLETIN l Vol. 11 I, No. 4, December 1999 ing plumage. We obtained good views of these While our records of the Aleutian Tern in birds in flight and perched as they fished to- Java, Bali and Sulawesi are not conclusive, we gether with other seabirds among and from the have presented our records here in order to numerous fish-trap platforms. Similarly, on 4 draw attention to a possible wintering area for December 1997 we also observed, from a boat this species and to encourage field workers a flock of approximately 35 probable Aleutian visiting Southeast Asia and Wallacea to be Terns during the late afternoon. They were more diligent in their examination of tern feeding just off the west coast of Bali, within flocks, especially from September to April. the maritime boundary of Bali Barat National Our records of a probable Aleutian Tern in Park. On 13 December 1997 we observed a Indonesia together with previously published group of 15 probable Aleutian Terns and observations of this species elsewhere in Crested Terns (Sterna be@) fishing at the Southeast Asia suggest that a significant pro- mouth of the Bone River, Gorontalo, Sula- portion of the western Pacific population of wesi. At the same time, about 200 unidentified Aleutian Tern migrates along the southern terns were feeding offshore along the interface coast of China and Southeast Asia to winter between the muddy river water and the clear in the islands of Indonesia and possibly the sea. Philippines. We observed the flocks closely for lo-30 minutes, as two of the flocks of the birds often ACKNOWLEDGMENTS fed close to our boat. N.l?H. is familiar with We are most grateful to P. Kennerley for his invalu- the species on its breeding grounds and has able comments on our manuscript. observed it twice in Alaska and once in Si- LITERATURE CITED beria. Both of us are familiar with the black- billed race of Common Tern (Sterna hirundo AMERICAN ORNITHOLOGISTS’ UNION. 1998. Checklist of longipennis), which the Aleutian Tern most North American birds, seventh ed. American Or- nithologists’ Union, Washington, D.C. resembles. All the birds we saw appeared to BRAZIL, M. A. 1991. The birds of Japan. Christopher be adults in winter or near winter plumage Helm. London, U.K. with a sharply defined pattern of extensive CAREY, G. J., D. A. DISKIN, I? J. LEADER, M. R. LEVEN, white forehead, with white extending onto the R. W. LEWTHWAITE, M. L. CHALMERS, l? R. KEN- crown of some individuals creating a bald- NERLEY, AND V. B. PICKEN. 1996. Systematic list. headed appearance. Some individuals had a Hong Kong Bird Report 1995:45. black nape with whitish streaking in the upper CAREY, G. J., D. A. DISKIN, V. B. PICKEN, AND P J. LEADER. 1995. Systematic list. Hong Kong Bird edge of the black nape (for an example see Report 1994:53. photographs 6 and 10 in Kennerley and Ol- DIXEY, A. E., A. FERGUSON,R. HEYWOOD, AND A. R. lington 1998). The wings and back were dark TAYLOR. 198 1. Aleutian Tern on the Farne Islands. grey with a contrasting pale rump and tail. Brit. Birds 74: 41 l-416. The bill was black on all the birds as were the HARRISON, F? 1983. Seabirds an identification guide. legs of perched birds off the west coast of Croom Helm Ltd., Beckenham, Kent, U.K. KENNERLEY, I? R., I? J. LEADER, AND M. R. LEVEN. Java. Flight appeared to be slower than that 1993. Aleutian Tern: the first records for Hong of a Common Tern and feeding was accom- Kong. Hong Kong Bird Report 1992: 107-l 13. plished more by dipping, similar to Chlidon- KENNERLEY, I? AND R. OLLINGTON. 1998. Aleutian ias terns or the tropical Sooty and Bridled Terns in South-East Asia. Oriental Bird Club Bull. terns (S. fuscutu and S. anuethetus). Unfortu- 27:34-41. nately we did not take note of the underwing LEE, D. S. 1992. Specimen records of Aleutian Terns from the Philippines. Condor 94:276-279. pattern which Kennerley and Ollington (1998) LEVEN, M. R., G. J. CAREY, AND V B. PICKEN. 1994. and Kennerley (pers. comm.) demonstrate to Systematic list. Hong Kong Bird Report 1993:50. be a diagnostic field identification character RAJATHURAI, S. 1996. The birds of Batam and Bintan for the Aleutian Tern in winter plumage. Islands, Riau Archipelago. Kukila 8:86-l 13.