Birds of Singapore
by the Bird Society of Singapore
Stercorarius pomarinus
Family: Jaegers and Skuas · Status: Vagrant · Size: 47–61.5 cm · Conservation: Least Concern
Breeds in the Arctic, across coastal tundra in the far north of Alaska, Canada, and Russia. Outside breeding season, it disperses widely to virtually everywhere with tropical and subtropical oceans.
The largest and heaviest of the three jaegers, with a noticeably barrel-chested build and broader wings than Parasitic or Long-tailed Jaeger. Adults occur in light and dark colour morphs. On the breeding plumage of the light morph, the face and cap are black, upperparts are brown except for a pale yellow band wrapping around the nape to the sides of head. Underparts are white except for a thick brown breast band and a dark vent. The rarer dark morph simply appears grey or brown all over. Breeding adults have broad, blunt, twisted central tail feathers extending beyond the other rectrices, which are diagnostic for this species when present. Non-breeding adults and immatures lose the twisted rectrices and become heavily barred above and below. In all plumages, Pomarine Jaeger shows the largest amount of white on the wings compared to the other jaegers. The upperwing typically shows 6-8 prominently white shafts on the outermost flight feathers, more than Parasitic or Long-tailed Jaeger. On the underside of the wing, the base of the primaries show the most white, appearing as a broad crescent, and a second crescent formed by white at the bases of the primary coverts.
Open seas, only encountered offshore.
A pelagic species that kleptoparasitises terns and other seabirds, snatching food in aerial pursuit. More vocal at sea than Parasitic Jaeger, and has comparatively slower wingbeats.