Kleptomania, and parasitism: they’re neither of them attractive words, or traits – and put them together, and you have something that sounds as though it would be most unpleasant.
Yet a kleptoparasite is the official name for birds like the great skua, which feeds by taking prey or other food from another bird that has put in the effort to catch its meal only to have it taken away at the last minute. The great skua can’t help it, though – it’s just made that way.
The great skua is an ‘interspecific’ kleptoparasite – that is, it’ll steal food from any other bird, not just its own kind (that would make it ‘intraspecific’). It’s also exceptionally aggressive – with a wingspan of around 125-140 cm, its roughly the size of the herring gull which is so familiar to us in Scarborough, and bears more than a passing resemblance to the juvenile of that species. And yet it’ll happily tackle a gannet to steal its dinner – and the gannet is our largest seabird, with a wingspan of up to 2 metres, and not averse to a bit of aggression itself given the right circumstances. No wonder the great skua is often called ‘the pirate of the seas’.
Its aggression extends to an even bigger and more dangerous creature – man. Approach the grass-lined nest, and you can expect trouble – the skua will fearlessly dive bomb, aiming at the head of the intruder. A wonderful painting by the Victorian marine artist James Clarke Hook shows a skua diving at a group of rockpooling children who have obviously had the misfortune to stray too close to its nest – you can see it here: bbc.co.uk/arts/yourpaintings/paintings/the-bonxie-shetland-51090
If all this kleptomania, parasitism and piratical behaviour paints a rather unsavoury picture of the skua, then consider this: the birds are remarkably good parents. They mate for life, and guard their chicks through a two-month fledgling process, with the fathers taking on a lot of the responsibility for feeding the youngsters.
The great skua migrates to the UK from the coasts of Spain and Africa, and can be found right round the coast, including off Scarborough, during its migration period in late summer and early autumn.
Its main UK nesting sites, though, tend to be further north – most of our population breeds on the Scottish islands, with over half the world’s great skuas on Shetland, while a few also nest on the mainlands of Scotland and Ireland.
It is part of a small family of birds, with four northern hemisphere species roughly divided into two main types – the chunky, gull-like great skua and the other three, all more tern-like in appearance being more streamlined and having tail streamers. These are the arctic, long-tailed and pomarine skuas. All can be seen off British shores, and each has a southern hemisphere equivalent.
The name skua probably originates from the Faroese word ‘skúvur’ – if so, it’s the only bird name from that language to have come into regular use outside the islands. It’s also known, rather charmingly, by its Shetland name of ‘bonxie’, a word with Norse origins. There’s an Old Norse word, ‘bunki’, which means ‘heap’, and the modern Norwegian word ‘bunke’ means ‘stack’, but apparently once referred to a dumpy woman – and the bonxie certainly has a stocky stature.
Although the great skua is mainly a northern bird, its very similar relative the south polar, or MacCormick’s, skua can be found at the South Pole, where it will attack penguins. Our exhibit, part of Scarborough Museums Trust’s taxidermy collection, can be seen in the community gallery at Scarborough Art Gallery until February 14 as part of Endurance and Survival, an exhibition curated by the Trust’s volunteers and paying tribute to the men of Ernest Shackleton’s Imperial Trans-Antarctic Exhibition a century ago.
The great skua is part of the Scarborough Collections, the name given to all the museum objects and artwork acquired by the borough over the years, and now in the care of Scarborough Museums Trust. For further information, please contact Collections Manager Jennifer Dunne on Jennifer.firstname.lastname@example.org or 01723 384510.