All species › Waders, gulls and terns › Jaegers and skuas › Pomarine Jaeger
Pomarine Jaeger | Stercorarius pomarinus
Middelste jager | Págalo pomarino
The Pomarine Jaeger is the heaviest of the three small jaegers that reach Australian and New Zealand waters from the Arctic tundra: barrel-chested, with a thick head, a heavy hooked bill and broad wings carrying a large white flash. The adult in summer plumage has two central tail feathers broadened at the tip into a twisted spoon — a feature no other seabird shows, but one the birds here have usually already lost. It chases terns and gulls until they drop their catch, but is just as ready to take prey itself.
Voice
In these waters it is nearly always silent. When it does call, it gives a hard gull-like kowk or geck as an alarm, and a mewing contact note between birds. On the northern breeding grounds it adds a series of harsh chattering throat notes and a call written as which-yew. An observer in the southern hemisphere will hear at most the short alarm, usually when two jaegers squabble over the same tern.
No freely licensed recording has been found for this species yet; what to listen for is described below.
Identification
A solid jaeger approaching half a metre, with a wingspan of over a metre and a weight of five hundred and fifty to well over nine hundred grams — half again as heavy as a Parasitic Jaeger. Build is the key: thick neck, broad chest, broad wings with a slower, heavier beat than the other two, and a notably thick two-toned hooked bill. A double white flash runs in the wing: six to eight of the primary shafts are white, more than in any other jaeger, and on the underwing a second pale crescent is added. The summer adult has two twisted spoon-shaped tail feathers projecting up to eleven centimetres; outside the breeding season these are short or broken and the tail then looks blunt. Morphs — pale with dark cap and breast band, dark sooty brown, and everything in between — vary so widely that they are no aid to identification; go on size, bill and flight.
Confusion species
Parasitic Jaeger (Stercorarius parasiticus) is the standing counterpart: about a quarter lighter, with a smaller head, narrower wings and a faster, falcon-like flight, and in the adult pointed rather than spoon-shaped tail feathers. Long-tailed Jaeger (S. longicaudus) is another half lighter than Parasitic, colder grey above, with very long thin tail streamers, a buoyant tern-like flight and only two or three white shafts, so that the wing flash barely shows. Brown Skua (S. antarcticus) and South Polar Skua (S. maccormicki) are true great skuas: heavier again, with a shorter wedge tail and a much larger white wing patch, and without the agile chasing flight. Juveniles of all three small jaegers are finely barred and closely alike; the weight of the bill, the breadth of the wing and the number of white shafts take you further than colour.
Habitat
In this region it is present only outside the breeding season, and then it is a seabird: the water over the continental shelf and the shelf break, and along open sandy coasts where terns and gulls fish. Unlike the Parasitic Jaeger it avoids sheltered bays and harbours; it is seen behind the surf of a long beach sooner than in an estuary. It follows trawlers and drifting shoals of baitfish, and on migration will sometimes cut across land along the coast. It breeds on wet Arctic tundra, far outside this map window.
Where the bird is most often found, arranged by main group and formation.
Range and movements
Breeds right around the North Pole, in Arctic Eurasia and North America, and winters at sea in the tropical and southern oceans. In Australia it has been annual in all ten of the measured years, with most records along the east and southeast coast from southeastern Queensland to the New South Wales-Victoria border, and besides these in tropical northern waters. In New Zealand it is a regular but not numerous visitor from December to April, centred on Auckland, south to Foveaux Strait and east to the Chathams — almost always off open sandy coasts and seldom in sheltered water. There are no records from Norfolk.
- Resident
- Breeding (summer)
- dark = core range, pale = thinly spread
Where and when to look
Between December and April stand on a headland along a long sandy coast and watch the build of the bird rather than its colour: a jaeger crossing behind the surf on broad wings with a slow beat, showing a thick, almost gull-like head, is this species. On a pelagic trip it will sometimes come to the berley, and then the double white flash on the underwing can be caught in a single photograph. Adults arriving early in the season may still carry the spoon tail; that is the one observation that admits no doubt.
Conservation
Least Concern (LC): the world population is large and the breeding range vast and largely unpeopled. The number of breeding pairs swings enormously from year to year, however, because on the tundra the species depends heavily on lemmings — in a peak year many pairs breed successfully, in a trough year whole districts skip breeding altogether. As a result the number of birds reaching the southern hemisphere varies from year to year too, and trends are hard to measure. For Australian and New Zealand waters there are no counts; what exists comes from seawatches and from the logs of pelagic trips.
Scientific name
Stercorarius pomarinus | (Temminck, 1815)
Temminck described the species in 1815 as Lestris pomarinus, in the first edition of his Manuel d'ornithologie; because it was later placed in another genus, author and year stand in parentheses. The type locality is Arctic Europe. pomarinus is a shortened form of pomatorhinus, from Greek poma, pomatos, 'lid', and rhis, rhinos, 'nostril': it refers to the horny cere that covers the nostrils at the base of a jaeger's bill. The genus Stercorarius was introduced by Brisson in 1760, after Latin stercus, 'dung'. Strikingly, genetic work shows that despite its name and size this species stands closer to the great skuas than to the other two small jaegers.