Adult Long-tailed Skua is an incredibly beautiful and elegant bird, guaranteed to 'make' any spring seawatch. Photo: Markus Varesvuo (www.birdphoto.fi)

To reach north Norway, Finland and Russia most have to pass close by the British Isles, and this is when we have a chance to see wonderful birds like Long-tailed and Pomarine Skuas, as well as their more common cousins, Arctic and Great Skuas.

Arctic Skuas breed across the whole Arctic region and migrate down to wintering areas off the coast of southern Africa and western South America each autumn. The first returning British birds are seen in early April at south coast headlands like Portland Bill, Dorset, and Dungeness, Kent. Numbers gradually increase to a peak in early May, when the passage consists mainly of skuas returning to Scandinavia, as these arrive at their breeding grounds later in the spring. This is reflected in the increasing proportion of pale-morph birds as spring progresses – this form predominates in the higher latitudes.

The larger Great Skua travels a much shorter distance to winter in the Atlantic off Iberia and north- est Africa, although some go as far south as West Africa and even Brazil. This species tends to migrate several miles out from the shore, and so is usually seen when blown towards land by strong winds. Most Great Skuas pass by west of the British Isles, but some travel up the English Channel and can be seen at sites like Dungeness, Kent, in small numbers. Great Skua is the first of the skuas to arrive, being seen from March with peak passage in mid-April. Immatures pass through later than adults.

Pomarine and Long-tailed Skuas are the real stars. These proud ‘pirates’ are the prize of any spring seawatch in their striking breeding plumage. Pomarine Skuas breed across Arctic Russia, Canada and Alaska and spend the winter well south in the South Atlantic and in the Pacific as far south as Australia. The Atlantic population of Pomarine Skuas favours areas with upwellings of cool water off the coast of Brazil and Argentina, or south-west Africa. They often follow fishing vessels for discarded fish.

These powerful, heavy birds start their return journey north in March, and by April many have reached the North Atlantic. Their movement off Europe takes most of them past western Ireland and round north-west Scotland, but they are usually too far offshore to be seen in any numbers, although strong onshore winds may bring them close. Some also pass up the English Channel and through the North Sea, and also along the Solway Firth (where 295 were logged in spring 1993).

Small groups and individuals can occur almost anywhere, especially with onshore winds, but it is the larger numbers which provide the real spectacle, and for these you have to go to some of the more remote birding places in Britain. Some massive spring movements have been recorded past the Western and Northern Isles, with more than 2,000 off Lewis, Outer Hebrides, on 7 May 2004, 1,147 past Balranald, Outer Hebrides, on 13 May 2003, and 2,093 at Wats Ness, Shetland, in May 1992.

Pomarine Skuas at Bowness, on the Solway Firth – one of the best British sites to see good numbers of this handsome pirate. Photo: Darren Robson

The slim, almost tern-like Long-tailed Skua breeds from Scandinavia eastwards through Siberia, Alaska and Arctic Canada as far as Greenland. The main wintering area for birds in the Atlantic is the Benguela current off Namibia and western South Africa, and an area off the Argentinian coast where the Falkland Current runs up the Patagonian Shelf. They start to move north in April, with the last leaving by early May, arriving in their breeding grounds from late May.

Some records of passage birds past these shores come from south and west Ireland, but most are from the Western Isles, and involve adult birds. The largest numbers have been seen from Aird an Runair, Balranald, in the Outer Hebrides, with 450 on 25 May 2002, 203 on 18 May 2004 and 164 on 18 May 2001. Other smaller parties have been seen from Lewis and Shetland.

Weather and timing

The key to successfully seeing these birds is the weather. Good onshore winds are needed at the time the birds are passing by, and this applies to all four species. Go equipped for a day’s seawatching, taking a seat if required, and be prepared for a wait.

In the English Channel the best conditions for Pomarine Skua passage are light southeasterly winds during the last week of April and the first three weeks of May. Great and Arctic Skuas can also be seen passing through, but will usually be earlier, in April.

In the Outer Hebrides, birds can pass to the west of the islands or to the east, through the Minch. Again, onshore winds in the middle two weeks of May offer the best chance for both Pomarine and Long-tailed Skuas.

Where to watch

These are some of the best sites for seeing Pomarine Skuas; those marked with an asterisk are also good for Long-tailed Skuas.

Scotland

• Dumfries and Galloway: Newbie (NY 178647)
• Western Isles: Aird an Runair, Balranald, North Uist (NF 687705)*
• Shetland: Wats Ness (HU 172505)*

England

• Kent: Dungeness (TR 095170)
• East Sussex: Selsey Bill (SZ 850923)
• Dorset: Portland Bill (SY 675683)
• Cumbria: Bowness on Solway (NY 224628)

Wales

• Anglesey: South Stack (SH 205825)
• Gwynedd: Criccieth (SH 498377)

Ireland

• Co Galway: Silver Strand (M 230232)