Masked Booby Sula dactylatra 藍臉鰹鳥
Category I. Accidental in offshore waters.
IDENTIFICATION
Feb. 2022, Mexico. Yann Muzika.
74-86 cm. The largest booby, adults are white with dark brown tail, primaries, secondaries, secondary coverts and tertials; the bill and eye are yellow with black around base and eye. Differs from adult Red-footed Booby in having yellow bill, red feet, dark tertials and in lacking black carpal on underwing.
Juveniles are dark brown to blackish apart from white breast and upper mantle that forms a broad collar. Older birds acquire dark brown and white feathers.
VOCALISATIONS
Rarely vocalises away from breeding grounds. None heard in HK.
DISTRIBUTION & HABITAT PREFERENCE
Occurs at sea.
OCCURRENCE
The sole record was of an immature off Po Toi on 18 March 2008 (Welch 2011).
BEHAVIOUR, FORAGING & DIET
No observations.
RANGE & SYSTEMATICS
Breeds in tropical and subtropical areas of the west and east Indian Ocean, the Pacific and west Atlantic (Grace et al. 2020). In China has also occurred in Fujian and Taiwan (Liu and Chen 2020).
Four subspecies are recognised. S. d. personata, which occurs in the south and east parts of the Indian Ocean and across the Pacific, is most likely to occur in HK.
CONSERVATION STATUS
IUCN: Least Concern. Population trend decreasing.
Grace, J., D. J. Anderson, C. Carboneras, D. A. Christie, F. Jutglar, E. F. J. Garcia, and G. M. Kirwan (2020). Masked Booby (Sula dactylatra), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.masboo.01
Liu, Y. and Y. H. Chen (eds) (2020). The CNG Field Guide to the Birds of China (in Chinese). Hunan Science and Technology Publication House, Changsha.
Welch, G. (2011). Masked Booby Sula dactylatra off Po Toi Island: the first Hong Kong record. Hong Kong Bird Report 2007-08: 223-227.
