The European eagle owl was first spotted by stoneworkers repairing the exterior masonry on the colonnade beneath the huge dome. They found droppings, then noticed a pair of eyes gazing steadily at them from a dark recess. The owl then flew off towards the bell tower, revealing a wingspan of about five feet.
Clerk of The Works Terry Lee said: ''It's not actually been living here, but it has been in and out over the last two months. If it stops the pigeons from fouling the cathedral and its surroundings we're delighted to have it here.''
Mike Everett, a spokesman for the Royal Society for the Protection of Birds, identified the visitor as a European eagle owl from a photograph. It is a species which is widespread in Europe but not resident in the British Isles.
''Quite a few are kept in captivity here, and they're popular with falconry centres where they're shown off to the public,'' he said. ''I'm sure it is one which has escaped.''
''They're big, tough, versatile birds and they'd have no trouble at all catching pigeons, of which there's an endless supply. It'll be taking them while they roost at night, and I reckon it could survive for ages.''
Eagle owls normally make their nests in rocky crevices on cliffs and mountainsides, and the nearest place they are found in the wild to Britain is in the mountains of the Ardennes in Belgium.