Ornithologists in the dark about mysterious decline of British owls

Mysterious, mournful, malevolent; but also wise, warm and wonderful. A raft of adjectives is needed to capture the complex emotions aroused in us by owls, perhaps the most enigmatic of all wild birds.

Mysterious, mournful, malevolent; but also wise, warm and wonderful. A raft of adjectives is needed to capture the complex emotions aroused in us by owls, perhaps the most enigmatic of all wild birds.

But another word is becoming appropriate: declining. For the country's five native owl species seem to be steadily falling in number, and their nocturnal habits make them difficult to observe.

A huge research effort to chronicle numbers and causes for their decline is being organised by the British Trust for Ornithology (BTO), which launched an appeal yesterday.

The species under the spotlight will be the tawny owl (the most common), the barn owl (the most rapidly declining), the short-eared owl (the least numerous), the long-eared owl (the most elusive) and the little owl (the most recent arrival).

Recently, Britain has boasted a sixth nesting wild species, the spectacular snowy owl of the Arctic, several of which bred for a number of years in the 1960s and 1970s on Fetlar, an island in Shetland, only to disappear.

The BTO says the research is urgent to make sure other species don't go the same way. "It is really quite scandalous how little we know about our populations of tawny and other owl species," said Humphrey Crick, the BTO's senior ecologist. "If we're not careful, they could begin to disappear without anybody really noticing."

The research effort will focus initially on three species. Two, the barn owl and the short-eared owl, are already birds of conservation concern. The barn owl's decline has been the most notable, with a population estimated at 4,000 to 5,000 pairs, less than half the number of 50 years ago. The fall is largely due to intensive farming, in particular the disappearance of unimproved grassland harbouring its main prey, field voles.

Less is known about the short-eared owl - there are about 2,000 nesting pairs mainly in the north and west of Britain - but it has a contracting range as well as a falling population.

The third species is the tawny owl. It is our commonest but there is increasing evidence that its numbers have tumbled in the past decade, so the BTO is organising a survey. It is seeking to raise at least £85,000.

Owls are increasingly liked today, and not just because of Harry Potter, says Mark Cocker, an ornithologist and author who publishes Birds Britannica, a compendium of bird folklore, next year. He thinks people are fascinated by owls largely because they are birds of the night, but says we now also associate them with beauty and wisdom. "It is this irreducible mystery in owls, troubling and captivating, that compels our attention and has more recently awakened our affections."

* Cheques, made payable to BTO, should be sent to BTO Owl Appeal, The Nunnery, Thetford, Norfolk, IP24 2PU; telephone 01842 750050 to make a credit-card donation; or give online at www.bto.org. Birds Britannica will be published in 2005 by Chatto and Windus.

SPECIES UNDER THREAT

Barn owl (Tyto alba)

This owl, pictured, is white underneath and seen over grassland as it hunts. Rapidly declining as intensive farming kills off the voles on which it feeds.

Tawny owl (Strix aluco)

Our most familiar owl, not least from its two calls: the musical hoot of the male ("tu-whoo"), and screech of the female ("tu-whit"). Encountered in cities; a pair breeds in the Buckingham Palace gardens.

Short-eared owl (Asio flammeus)

In some ways the easiest of the native owls to observe closely because it often hunts by day on moorlands where it lives.

Long-eared (Asio otus)

The most elusive owl. Hard to spot even in the day, or when gathered in roosts. The "ears" after which it is named are not ears but tufts of feathers.

Little owl (Athene noctua)

Introduced to Britain in the 19th century. Celebrated in Greece, where it is the symbol of Pallas Athene, the goddess of wisdom (thus the wise old owl). Doing well but could suffer under changing farming practices.

Snowy owl (Nyctea scandiaca)

Bred in Britain from 1967 to 1975 on Fetlar island in the Shetlands. The male left in 1976 and two females followed in 1993.