WEEK-BY-WEEK BIRDS TO SEEK: WEEK 29 SKUAS

EVERY WEEK IN 2017 WE WILL HAVE NEW SUGGESTIONS FOR A DIFFERENT GROUP OF BIRDS TO LOOK FOR TO HELP DEVELOP YOUR #MY200BIRDYEAR LIST

This week, it is Skuas

Skuas are close relatives of gulls, which specialise in bullying other seabirds to make them regurgitate their fishy catches (kelptoparasitism). There are four British species, two of which (great Skua and Arctic Skua) breed in northern Scotland and some Scottish islands and are regularly seen around the coasts. The other two (Pomarne and Long-tailed Skuas) are scarcer to rare, and are usually seen on passage in May and autumn. The Great Skua, aka Bonxie, is quite distinctive and relatively easy to identify, while the three smaller species are notoriously similar to each other and a big pitfall for the unwary. Practice in the field is the only way to get better at indentifying smaller skuas.

Great Skua

Great Skua

Great Skua

The Bonxie (to give it its Shetland name) is about the size of a Herring Gull: big and powerful and pretty uniformly brown all over, apart from obvious white ‘flashes’ in the wings, which can be seen even at great range at sea. Deep chested and short tailed, the impression is of a dark immature gull with long wings and a powerful flight on deep wing beats. Bonxies parasitise larger seabirds, including Gannets.  Found in small numbers round the coast out of the breeding season.

 

Arctic Skua

Arctic Skua, pale morph adult

Arctic Skua, pale morph adult

Arctic Skua, dark morph adult

Arctic Skua, dark morph adult

Arctic Skua, pale morph juvenile

Arctic Skua, pale morph juvenile

Notably smaller than a Bonxie, the Arctic Skua is the commonest of the smaller skuas. Two main colour morphs (dark and light). Adults have mid-length, pointed central tail feathers and (on pale morph adults) a neat contact between the dark underwing and the pale belly. White flashes are obvious.  Juveniles and immatures are tougher to identify, but look slim (not chunky like Pomarines) but not tern like (like Long-tailed Skuas). Arctic Skuas chase terns and Kittiwakes. Youngsters can often have rusty fringing (unlike the colder tones of the other two smaller species).

 

Pomarine Skua

Pomarine Skua, pale morph adult

Pomarine Skua, pale morph adult

Very like a slightly bigger, deeper chested, chunkier Arctic Skua in all plumages. Pale morphs predominate. Adults have long, spoon-shaped central tail feathers (which may be absent), and a smudgier contact between the dark underwing and the pale belly. Pomarine Skuas bully Common Gulls and the like .Juveniles are usually colder in tones with a double wing flash on underwing and extensively barred tail coverts.

Long-tailed Skua

Long-tailed Skua,  adult

Long-tailed Skua,  adult

Long-tailed Skua, intermediate morph juvenile

Long-tailed Skua, intermediate morph juvenile

The rarest of the four, the Long-tailed Skua is also the smallest, most tern-like skua species. Adults with complete tails are easily identified but their very long central tail streamers, lark of dark shoulder stripe and small slim shape. Juveniles are like small, slim versions of Pomarines Skuas, but with much smaller bills and only hints of white flashes (especially on upperwing, where only outer shaft is white).

All photos from Alamy