Pomarine Skua Stercorarius pomarinus

Pomarine Skua
Photo © Nial Moores

Nine records by Nial Moores, involving ca 27 individuals, in March, May, and again in September, October and November. Largest day count was 10+ on November 4th 1995, seen between Busan and Daema Do/Tsushima (with many more in Japanese waters). At least one, a juvenile on October 8th 2001, seen with another experienced observer (Charlie Moores). Subsequently, two other experienced observers (Arnoud van den Berg and Magnus Robb) saw at least 200 per hour passing south within sight of land from the Guryongpo peninsula on the east coast on October 19, 2002, with 100 per hour on October 20th. Several photographs were taken.

The Pomarine Skua appears to be the most numerous skua in Korean waters, as it is in Japan (Brazil, 1991), and as such its omission from the Korean list seems surprising. Although individuals of several ages have been noted (including adults with full "spoons"), by mid-2002 only one individual has been satisfactorily photographed (though that from a moving boat, with a hand-held camera focused down the binocular eye-piece).

The photographed pale phase individual shows (1) the typically heavy structure of Pomarine Skua (somewhat intermediate between that of the scarcer Arctic Skua Stercorarius parasiticus and the rather rarer South Polar Skua Stercorarius maccormicki.), along with (2) barred uppertail coverts; (3) an all dark cap, reaching down to the bill base, and (4) an obviously two-toned bill, with a blue grey base and a blackish distal third (all diagnostic of this species). The underwings appeared largely dark, suggesting, in combination with other features that it might probably be best aged as a subadult, possibly 3rd calendar year).

4 Pomarine Jaegers, October 20, 2002. Guryong-po Peninsula,
Photo © Arnoud van den Berg

Four birds photographed from Guryongpo during a movement of many hundreds of Pomarine Skuas on 19 and 20 Oct.

Based on extensive experience of the species in the UK and in Japan, additional pointers favoring Pomarine are (5) its barrel-shaped body, (6) its bowed wings, (7) its heavy tail, angled downwards, (8) its strong pectoral band, with distinctive contrasting collar, suffused with buff or yellow, and (9) the extent of white in the primaries (with some white also showing on the primary coverts: a feature often shown more strongly by South Polar).

While records in Japan show a similar pattern of occurrence (with highest numbers in October and November, with a smaller peak in May) the present bias in records in Korea towards the spring and especially the autumn is likely also to be strongly influenced by the timing of migrant-survey visits to outlying islands. As noted in Brazil (1991) Pomarine Skuas are often associated with Black-legged Kittiwakes Rissa tridactyla, a common winter visitor along the east coast, even occurring in small numbers as far west as Gageo Island. Mid-winter boat trips would help to further clarify the real status of this species in South Korea.