Pomarine jaeger

Voice

Away from the colony it is silent: a bird passing the Dutch coast goes by without a sound, and that is the normal picture. On the Siberian tundra territorial flights produce a hoarse, barking wek-wek, and attacks on intruders a short nasal note. Since European contact with the species is almost entirely a matter of seawatching, its voice is of no practical use to the field observer here.

Identification

Bulky and barrel-bodied, with a broad wing base, a heavy head and a thick, clearly bicoloured bill whose dark tip covers about half its length. The wingbeats are slower and stiffer than a Parasitic Jaeger's and the silhouette suggests a small Great Skua rather than a gull. Pale adults show a black cap, yellow neck sides, a broad and solid dark breast band and heavily barred flanks and undertail coverts; the two central tail feathers are elongated, widened at the tip and twisted about their axis so that they read as spoons or blobs — by autumn they are often broken or moulted. Juveniles are colder greyish brown than a young Parasitic, with a notably plain head, strongly barred upper- and undertail coverts and a blunt tail projection; the best feature at that age is the double white flash on the underwing, formed by pale primary bases together with pale greater primary coverts.

Confusion species

Parasitic Jaeger is slimmer, with a narrower hand, faster wingbeats, a finer bill and pointed straight streamers; its juveniles are warmer rufous, have a clearly streaked head and show only a single white flash on the underwing. Great Skua is larger and broader still, uniformly dark brown, with no pale underparts and far bigger white wing flashes. Long-tailed Jaeger is much smaller and finer, with a grey mantle and almost no white in the hand. A heavy dark jaeger with a double underwing flash and a thick pale bill base in October is almost always this species.

Habitat

It breeds on wet, low-lying coastal tundra in Siberia and North America, hunting lemmings almost exclusively; in poor lemming years it does not breed and spends the summer wandering at sea. It winters on tropical and subtropical seas, usually over the continental shelf and not far from land. On migration it robs gulls and auks of their catch, takes carrion and regularly follows fishing vessels — unlike the Long-tailed Jaeger, which seldom joins them.

Range and movements

It does not breed in Europe; all European records concern migrants from Siberia and Greenland. Along the Dutch coast October and early November are the core of the season, in strongly variable numbers: several hundred birds in an irruption year, a few tens in a poor one. In Spain it is seen mainly off the Basque and Galician coasts and through the Strait of Gibraltar, with an autumn peak in October and November and the occasional wintering bird.

• Breeding (summer)
• Winter
• Passage
• Migration direction
• dark = core range, pale = thinly spread

Where and when to look

Wait for the weather rather than the date: a firm westerly to north-westerly of force 6 or more in the second half of October gives the best odds, especially around a rising tide. Choose a watchpoint with deep water close inshore and scan low over the waves — Pomarine Jaegers fly heavily and in a straight line, often clear of the stream of gulls. In irruption years adults may linger for days over shallow fishing grounds such as the Bruine Bank and are better seen from a boat than from the beach.

Conservation status

Least Concern globally, with a large but strongly fluctuating world population. The numbers reaching Europe depend almost entirely on the lemming cycle in Siberia, and the weakening of that cycle under milder, wetter Arctic winters is the main long-term concern. At sea, bycatch in fisheries is a local factor but does not drive the trend.