Unusual visitor wings its way in to meet the native gulls

A STRANGE gull has taken up residence in the centre of Dublin. I have not seen the celebrity myself but Eric Dempsey, who runs the Birds of Ireland News Service (BINS) and is an authority on rare birds, has been keeping tabs on the visitor.

Speaking on RTÉ’s Mooney show, he described it as a medium-sized bird, “coffee coloured with white wings”. It hangs around the pond in St Stephen’s Green, where it fraternises with the ducks and native black-headed gulls, and has also visited the Financial Services Centre on the Liffey quays. Telling vagrant gulls apart is a task for experts like Eric, who has identified the foreigner as a young Iceland gull. Unlike our native gulls, with their black wing-tips, the Iceland gull has no black on the wings. This is its most obvious distinguishing feature.

Feathers are made of keratin, fingernail material, which is quite soft. The long ones of the outer wings are the bird equivalent of fingers. The tips constantly brush against objects, causing them to become frayed and worn. In the case of gulls, the rough rocky places they frequent make wear a constant problem. A coating of the black pigment melanin strengthens the feathers and renders them much more durable and so most gulls have black wing-tips. If you live in the Arctic, however, black patches on any part of the body make you conspicuous against a background of snow and ice. Dark wing-tips are easily spotted by predators, such as sea eagles. So serious is the danger that the gulls of Arctic regions are white all over.

The Iceland gull is misnamed. Although it’s a common bird in Iceland and you will see this elegant seabird if you visit the docks in Reykjavik in winter, the species does not breed there. Why it refuses to do so is a mystery but the bird seems to bear a grudge against the country after which it is called. It used to breed on Jan Mayen, a remote island to the northeast of Iceland, but the nearest nests today are on rocky coasts in Greenland. There are also colonies on Baffin Island and on the mainland coast of Quebec.

At the end of the breeding season, Iceland gulls move southwards and eastwards towards Scandinavia. A few stragglers, usually young birds such as the Dublin one, turn up in Ireland. Although Iceland gulls don’t breed until they are three years old, the youngsters always move north again in the spring.

Gulls are resourceful. Great-blacked gulls force other seabirds to disgorge food, while black-headed gulls have learned to follow the plough, devouring the worms exposed when the soil is turned. But all of our Irish gulls, with the exception of the kittiwake which spends most of the year well out to sea, are “picaroons”, an old Dublin name for people who rummage through refuse looking for items to salvage. Gulls visit the centres of cities, picking up discarded food. Iceland gulls will scavenge occasionally but this is not their lifestyle of choice. They prefer fresh fish, which they catch by plunge-diving, a technique used by those smaller relatives of gulls, the terns. Catching prey directly is unusual for such a large gull, although the lesser black-backed, one of our larger native ones, also plunge dives.

There are between 45 and 51 species of gull in the world. It may seem odd not to give a more precise figure, but the experts argue as to whether some candidates should be regarded as full species or treated as varieties of existing ones. Ornithologists tend to be either “lumpers” or “splitters”. Lumpers are reluctant ever to bestow the coveted title of “species”, whereas splitters want to give every avian Tom, Dick and Harry the honour. Classifying gulls is particularly difficult, there are some many variations and intermediate forms. During the ice-ages of the last two million years, gull populations became isolated geographically, each developing its own peculiarities. When the ice melted, birds from differing populations no longer interbred but, even so, varieties which look quite different are sometimes closely related. Our native herring gull, for example, has light grey wings while the lesser black-backed’s wings are a darker slate grey. The leg colours, lifestyles, and perhaps even personalities, of the two birds differ. Yet, individuals, very occasionally, interbreed in the wild. In an experiment where eggs were interchanged in the nests of the two species, the young fledged successfully and went on to hunt normally. However, when they reached breeding age, the youngsters tended to choose members of the “wrong” species as nesting partners. The experiment suggests that even these apparently dissimilar gulls are, in fact, very closely related.

The Irish bird-watcher is spoilt for choice as far as gulls are concerned. Although they are found almost everywhere in the world, the largest concentrations of gulls are in cool northern coastal areas, making Ireland an ideal location for sightings. Vagrant gulls from the Arctic, and wanderers from North America blown off course by storms, make landfalls along our shores. At least 18 different kinds of gull have been recorded here, more than a third of all the gull species in the world. It is appropriate, therefore, that the name “gull” should be derived from Irish; gulls are so called “mar bíonn siad ag gol”.

* For the latest information on rare and unusual bird visitors, contact BINS at 1550.111700.