Few rich pickings from diving bird’s diet
On the move: cormorants are heading inland. Illustration: Michael Viney
The limply outstretched wings of the just-about-upright cormorant can express how many people feel at the end of another hot day. But they can also challenge one’s sense of fitness in nature; diving birds surely shouldn’t have to do that.
But this is to judge from Irish experience alone. Move to Florida and there are subtropical cormorants, the scrawny anhingas, or “water turkeys”, doing much the same, along with pelicans, brown and white. Elsewhere, there are storks and turkey vultures that, while not needing to swim underwater, might also imitate broken umbrellas.
Wing-spreading can have different reasons in different birds but our northern cormorants are just doing the weirdly obvious and drying their wings. Letting themselves get wetter does let them dive deeper and stay under for longer. This is not from any lack of oil from the birds’ preening glands. In the structure of their feathers, the outer layers let water in, but the inner layer holds air for insulation. This let the so-called Great Cormorant spread northwards into colder waters, spreading its wings to dry even in Greenland.
Ireland’s native subspecies of Phalacrocorax carbo is the Atlantic cormorant, also the bird of the north of France, Britain and Norway. But mainland Europe has another subspecies, slightly smaller, its plumage glossed blue-green rather than purple, and with sinensis tacked on to its name. The two kinds together are now more numerous than at any time in the past 150 years – at least 520,000 are wintering in Europe – and this dramatic growth, overwhelmingly of sinensis, has led to fierce conflict with fish farmers and demands for EU-wide control.
In spring and summer, many of Ireland’s cormorants are gathered at or around their breeding grounds within commuting distance of Dublin Bay. About 2,000 pairs nest on islands off the north of the county – St Patrick’s, off Skerries, on Lambay, and also on Ireland’s Eye. Their nests are spaced out on steep slopes above cliffs, or on rocky terrain. On Bray Head, a rare mainland colony, keeping to the cliffs gives security from foxes and rodents, as do trees on islets in some lonely lakes in the west.
Even with protection under the Wildlife Act, our cormorants have flourished only modestly, with sharp declines at some traditional breeding colonies, especially on west and south coasts, and increases at others. The past 50 years, however, have seen a marked move to inland waterways in winter, much to the concern of anglers in the midlands.