Christmas Frigatebird Fregata andrewsi 白腹軍艦鳥
Category I. Accidental in sea areas.
IDENTIFICATION
Identification of frigatebirds is complex, and the full variation cannot be covered here. Readers are referred for further details to James (2004), from which the following is taken.
Oct. 2019, Sabah, Malaysia. Dave Bakewell.
89-100 cm. Adult males have white oval on belly with axillary spurs on some birds.
Nov. 2018, Sabah, Malaysia. Dave Bakewell.
Adult females have black throat, largely white underparts and distinct white hind collar with white axillary spurs that are angled forwards or parallel-sided. Third-year males have extensively white belly, mottled axillary spurs and breast tabs; females have black throat and white lower belly only.
Juveniles (illustrated) have very prominent alar bars (on the upperwing), a hexagonal white belly patch and usually parallel-sided or forward-angled axillary spurs that originate behind line of breast band. Second-year birds have black breast tabs, white belly lacking outline of black belly point, axillary spurs that, if present, are parallel-sided or angled slightly forwards and prominent whitish alar bars.
VOCALISATIONS
Usually, silent away from breeding colonies.
DISTRIBUTION & HABITAT PREFERENCE
Recorded mostly at sea, but records also from Tsim Bei Tsui and Mai Po.
OCCURRENCE
1981: an immature in East Lamma Channel on 5 September 1981.
1985: an immature at Tsim Bei Tsui on 5 May.
1993: an immature at Cape D'Aguilar on 25 September 1993 in the aftermath of a tropical storm.
1996: an immature near Sha Chau on 6 August 1996.
1997: a first-stage bird at Mai Po on 10 March 1997.
2007: an adult male at Tung Ping Chau on 21 April, and an immature off Lamma on 4 October.
BEHAVIOUR, FORAGING & DIET
All records have only occurred on one day.
RANGE & SYSTEMATICS
Monotypic. Breeds on Christmas Island in the east Indian Ocean; forages in surrounding ocean and disperses widely from Sunda Shelf to South China Sea and Gulf of Thailand (Orta et al. 2020). In China recorded in sea areas from Fujian to Hainan (Liu and Chen 2020).
CONSERVATION STATUS
IUCN: CRITICALLY ENDANGERED. Population of 2,400 to 4,800 birds breeds on only one island and is declining.
Orta, J., E. F. J. Garcia, G. M. Kirwan, and P. F. D. Boesman (2020). Christmas Island Frigatebird (Fregata andrewsi), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.chifri1.01
James, D. J. (2004). Identification of Christmas Island, Great and Lesser Frigatebirds. BirdingAsia 1 (2004): 22-38.
Liu, Y. and Y. H. Chen (2020). The CNG Field Guide to the Birds of China (in Chinese). Hunan Science and Technology Publication House, Changsha.
