Cormorants flush for success

Researchers at the School of Biosciences at the University of Birmingham have discovered that Cormorants' underwater vision is no better than that of humans. Instead, they have found that the birds flush out prey by disturbing it, rather than pursuing it at speed.

Until now it has been a mystery as to how Cormorants are able to catch fish regardless of whether the water is crystal clear or murky. Professor Graham Martin and his team from the University's Centre for Ornithology have found that Cormorants are the underwater equivalent of herons, taking prey only at short range and by stealth, flushing fish out from hiding places and grabbing them with a rapid lunge of the neck.

Professor Martin explained: “Cormorants are often seen as mysterious birds with a vicious beak. They are disliked by anglers, while in China and Japan they are cherished pets, trained to catch fish for the pot. We thought that Cormorants were the underwater equivalent of eagles or hawks, seeing prey at a distance and hunting it down at high speed, but that would require excellent vision. Now we see them as something quite different – highly manoeuvrable, wily birds with lightning reactions, capable of grabbing something at short range as it tries to escape.”

An extra trick that Cormorants have developed to help them with their efficient feeding is their ability to move their eyes and see between their beaks. Professor Martin continued “Not many birds can see what they are holding in their mouth – most birds see just beyond their beak tip, much as we see just beyond our nose. Cormorants, however, can swing their eyes forward to see what they are holding. This may be an essential part of their success, since they may often grab something barely seen as it tries to escape when flushed out. Cormorants will need to bring it to the surface to check it out before swallowing.

“We are full of admiration for these birds and the way that natural selection has led to their poor underwater vision being complemented by their artful fishing technique.”

Photo: Steve Young (www.birdsonfilm.com)