Pacific loon

Voice

In Europe practically always silent; birds that strand here are rarely heard. On the breeding lakes it gives a hoarse, repeated series kok-kok-kok-kok, a deeper, barking kwow and long wailing calls that rise in pitch. When uneasy a short, hard kwak, and in flight now and then a hoarse note recalling Black-throated Diver.

Identification

Slightly smaller and more compact than Black-throated Diver. The bill is thin, straight and fairly short, and is held level, never tilted up. The head is round and smooth, with the bulk behind the eye, so the nape looks bulging and puffed and the forehead runs on evenly. In winter the border between the dark hindneck and the white foreneck is straight and crisply drawn, and many birds carry a thin dark band across the white throat, the so-called chinstrap. The hindneck is often strikingly pale, at times almost silvery grey, standing out lightly against the darker back. The rear flanks stay dark down to the waterline. Young birds usually add a complete dark bar across the vent. In summer plumage the hindneck is pale pearl-grey and the throat carries a black-purple patch.

Confusion species

Black-throated Diver is where the confusion nearly always starts: it is about a tenth larger and heavier in build, with a stouter bill often held slightly raised, a flatter forehead and a darker hindneck, and when swimming it shows a white oval patch above the waterline on the rear flank. That flank patch is the most usable feature, provided the bird is riding calmly. The chinstrap argues for Pacific Diver, but is missing on about half of the young birds, so it counts only when you can see it. Red-throated Diver is smaller and paler, with an uptilted bill and a finely white-spotted back. Great Northern and White-billed Divers are far larger and heavier, with a thick bill and an angular head with a forehead bump; in White-billed the outer half of the culmen ridge also stays pale, which no small diver shows.

Habitat

Winters at sea, in bays, sounds and estuaries and usually closer inshore than the large divers, over sand and mud bottoms where it dives for small fish. Birds that reach Europe settle in harbours, off the surf line and sometimes for weeks on a large inland lake or reservoir. It breeds on lakes and pools in tundra and northern forest, preferring large clear waters with islets and little submerged vegetation.

Range and movements

Breeds in north-eastern Siberia, in the Aleutians, in Alaska and in northern Canada, and winters along the Pacific coast to Japan, Korea and Baja California. Within the area of this guide it is a true vagrant: there is no breeding population, no regular wintering and no passage. Most European records come from Britain and Ireland, where since 2007 birds have wintered in Cornwall, Yorkshire and Scotland, some returning to the same spot for several years. Beyond that there are scattered records from France, Spain and Scandinavia. For the Netherlands and Belgium it is a species to keep watching for, not one to count on.

Where and when to look

Look in December and January; those are the months in which the British wintering birds were nearly always found. Search within a group of Black-throated or Great Northern Divers off the coast or on a large inland water, and check the rear flank of each bird first: if it stays dark down to the waterline, it is worth looking further. Take up position early in the morning with the sun behind you and give it time, because the white flank patch of a Black-throated Diver comes and goes with the bird's posture and can only be judged after patient watching.

Conservation status

Not globally threatened (IUCN: Least Concern), with a world population in the order of a million birds and a stable trend. That figure says little for Europe: the species does not breed here and the few birds that appear are no measure of anything. In its own range the pressures are oil pollution along the wintering coasts, drowning in fishing nets and fluctuating water levels at the breeding lakes; warming of the tundra may also alter breeding conditions.