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 Ailsa Craig is a precipitous island at the mouth of the
Firth of Clyde, some 15 miles south of Arran. Throughout history its fame has rested on two quite distinct products: curling stones and young gannets. Basically a huge lump emerging from the sea, Ailsa
Craig's columns of granite consist of particularly fine-grained syenite, the perfect material for making the very best curling stones. Not surprisingly, the rock has
been quarried for centuries. The first published reference to Ailsa gannets appeared in 1583. "Elsay... is one grate high hill, round and roughe... and (with) an abundance of
Soland Geise". At that time the colony of birds was regularly raided to provide food that could be stored away for the lean days of winter.
The North Atlantic gannet (Sula bassana) is a large black and-white seabird about 3ft (1 m) in length. The adult is white, with a yellow wash over the crown and black wing tips. Its
long tapered tail is balanced by an equally long tapered neck, head and bill, giving the bird its peculiar spindle shape. The pointed wings are held stiffly and the gannet flies with a series
of flaps interspersed by stiff winged glides. This is a truly oceanic bird, wandering far from land; it makes use of the wind over the seas to generate lift and propulsion. The gannet
spends much of its fife at sea, where it finds its food by making spectacular aerial dives. The height of the dives varies from about 30-100ft, the bird often hovering over the sea before
closing its wings and plunging head first to grab its prey. Out on the water, a flock of diving gannets is thrilling, with birds plummeting into sight on all sides creating huge splashes.
These birds feed mainly on small fish, but larger prey, up to 1 Ib (500g) in weight, are caught and brought to the surface before they are swallowed completely. Just how much
fish a gannet requires each day to survive is unknown, but adult gannets on Ailsa Craig weigh between 5-7lbs (2.5-3.5kg), and are hardly likely to consume food equal to over half their body weight in a day.
With the whole of the North Atlantic as their feeding ground gannets are widely dispersed in winter, but by late January the early arrivals are back at Ailsa Craig, staking their claim to
the best nest sites. Most birds arrive in mid February and each individual seeks out the site that it used the previous year. Here it will be reunited with its mate gannets are faithful to
their home rather than their partner. Soon after their reunion the pair repair or rebuild their nest. Most gannets make much use of seaweed, although those on Ailsa Craig mainly use
grass to construct their nests. The birds are packed closely together and each pair has a territory that extends about as far as the birds can reach with their dagger-like bills. Along
the cliffs of Ailsa Craig each pair tends to occupy the top of a single granite column and there is an average of just over two pairs per square metre. Gannets make poor neighbours
and there is much bickering and squabbling, often set off when one pair steals nesting material from those next door.
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