Fast food dive-in

30 August 2000

Cormorants can catch fish up to 30 times faster than other seabirds. Their prey-catching skills enable them to survive in the icy Arctic without piling on insulating layers and waterproof feathers.

This recent finding by David Grémillet and Sarah Wanless from NERC's Centre for Ecology & Hydrology (CEH) runs contrary to the usual expectations of warm-blooded animals which live in cold climates. Animals such as seals and seabirds have thick waterproof fur or feathers and a layer of fat beneath the skin. They also tend to have a larger body size in cold areas.

In contrast, cormorants have very little body insulation and their feathers can become partially waterlogged. Cormorants from chilly Greenland are the same size as birds from European waters. The research comparing cormorants from France and Greenland also showed that arctic birds do not eat more than their southern relatives.

"The secret of their success," said David Grémillet, "is their skill in choosing places in cold waters where fish are plentiful. Even when they are rearing chicks, Greenland birds only spend 40 minutes diving each day." By contrast, cormorants breeding off the Normandy coast spend around 2½ hours diving each day.

Sarah Wanless added, "We saw this behavioural adaptation really pushed to the limit near Disko Bight in Greenland where currents keep the water ice-free. Over-wintering cormorants spent just 9 minutes on their daily fishing." This means that they are catching fish 30 times faster than the highest rate recorded for seabirds.

The research is of major relevance to the ongoing debate about the potential impact of European cormorants on fish stocks. Hunting and fishing lobbies in most European countries promote the idea that cormorants have an adverse effect on fish stocks. This study demonstrates that they do not need more food than any other fish-eating birds. But the research does provide evidence for one area of conflict. In Europe the wintering cormorants fly inland. It is not surprising that they favour well-stocked lakes and fish farms where food is plentiful and the water shallow to provide a convenient fast food outlet.

Further information

David Grémillet
Centre d'Ecologie et Physiologie Energétiques du CNRS de Strasbourg
Tel: 00 33 388 106 900 (From Monday 4/9/00.)

NERC Press Office
Natural Environment Research Council
Polaris House, North Star Avenue
Swindon, SN2 1EU
Tel: 01793 411561
Mob: 07917 557215

Notes

1. The Natural Environment Research Council (NERC) leads in providing independent research and training in the environmental sciences.

2. Sarah Wanless is at CEH Banchory and is funded by NERC. David Grémillet is based at the Centre d'Ecologie et Physiologie Energétiques du CNRS de Strasbourg. His work at CEH Banchory was supported by a TMR Marie Curie Fellowship of the European Union and a small research grant from the British Ecological Society.

3. This research is just one of the subjects featured in the Autumn 2000 issue of NERC News.

Press release: 15/00

Fast food dive-in

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