Monday, September 19, 2011
FOR several weeks my boat was marooned by an engine breakdown on the Royal Canal a few kilometres east of Mullingar.
The other day I was driving down the tow-path to check up on it when I noticed, out of the side of my eye, something strange in the water. A dark, snake-like object was moving down the middle of the canal.
It was, of course, the head and neck of a cormorant. Sometimes these birds have the disconcerting habit of swimming with their bodies submerged and only the head and neck in the air.
A cormorant in Co Westmeath isn’t such a strange phenomenon, increasing numbers of them are abandoning the sea and taking to fresh water. But I’d never seen one around here before, so I stopped the car to watch it for a while.
Cormorant watching can be an annoying experience. Just when you are about to get a good look at the bird it dives, and usually re-surfaces where you least expect it. But I was able to establish that it was a young bird that had hatched this year. Young cormorants are dark brown rather than the glossy blue-black of adults. It had obviously become recently independent of it parents and was pioneering new fishing grounds. A good supply of small to medium sized fish is vital to a cormorant. The reason more and more of them are abandoning the coast and turning up on rivers, lakes and canals is almost certainly because commercial fishermen have over-exploited coastal stocks and there are now more suitable fish in fresh water than in the sea.
They catch fish by using their webbed feet and streamlined bodies to swim under water at great speeds and they can dive to depths of up to forty-five metres. They grab them in their beaks and normally return to the surface to swallow them. When their crop is full they’ll return to a perch on a rock or tree and sit in a characteristic upright pose with their wings extended.
Why they do this has been the cause of bitter controversy among ornithologists. There have been many theories, two principal ones being that it helped them to digest the fish or it helped them to regulate their body temperature.
But recently a detailed study was undertaken to try and settle the argument once and for all. Its conclusion — and it was quite definite — was that they are doing the obvious thing — they’re drying their feathers.
Apparently as cormorants have evolved they have abandoned the waterproofing preen oils that most diving birds use to keep them dry. The reason for this was because the oils, and the tiny air bubbles they trapped, were slowing them down under water and making it harder for them to catch fish. So when they get thoroughly soaked they have to dry themselves off.
The bird I was watching is properly called the great cormorant. There is one other species found in Ireland, the shag. ‘Cormorant’ and ‘shag’ are names that are used quite indiscriminately for different members of the family around the world — our great cormorant is called a black shag in New Zealand.
Irish shags are slightly smaller than great cormorants and are green-black rather than blue-black. Unlike cormorants, they appear to loathe being away from the sea.
There are probably between 5000 and 6000 breeding pairs of great cormorants in Ireland, although I can’t find any recent census figures. They are amber-listed, meaning they are of medium conservation concern.
- dick.warner@examiner.ie
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