A grimace of pain flickered across the warden's face as an infuriated puffin clamped its beak around his hand with all the force the bird could muster.

David Steel, the chief warden of the Farne Islands, rapidly withdrew his hand from the puffin's burrow and was thankful that, on this occasion at least, the bird let go after a few seconds.

“They often remain latched on to your fingers after you've withdrawn your hand from their burrows,” he said, as he wiped away a drop of blood and surveyed the impression the sharp beak had left in his flesh. “It's a bite and a half.”

The encounter between man and bird was an early skirmish in the battle to count tens of thousands of breeding puffins over the next three months.

The Farne Islands provide visitors with one of the most spectacular views of nesting birds in Britain and at this time of year puffins can be seen in their thousands as they clean out their burrows, conduct courtship or just wait for eggs to hatch.

Puffins, with their brightly coloured beaks and ungainly walks, are the chief attraction, but the islands are home to tens of thousands of other sea birds including guillemots, shags, razorbills, and Arctic and roseate terns.

Feeling down a burrow for a parent bird, egg or hatchling is the tried and tested method for counting breeding puffins, which dig tunnels rather than build nests. Puffins mate for life and return to the same burrow each spring.

Burrows are often more than a metre long, so counters often have to push their arms in up to the shoulder before they can feel if it is empty or occupied. Some puffins will gently bat the hands with their beaks in warning, others bite hard.

Another problem is that the birds are hygenic creatures that build two chambers underground, one as living quarters, the other as a loo that fills with rank slime.

The National Trust wardens on the Farne Islands, off the Northumberland coast, will fumble around in burrows thousands of times over the next few weeks as they assess puffin numbers. It is a delicate, dirty and often painful task and they have to use their bare hands because protective gloves would increase the chances of breaking eggs or hurting the birds.

The islands host the fourth-biggest breeding colony of puffins in Britain and the largest in England.

Other sites, including the 500,000-strong St Kilda colony, have suffered in recent years as the birds struggle to find enough fish to feed their young, and the Farne Islands are becoming an increasingly important home for puffins.

In 1969 6,800 breeding pairs were recorded. The numbers rose to 55,675 in 2003 and this year it is anticipated that they will exceed 60,000.

Whereas the Farnes have recorded a consistent rise since counts began 40 years ago, other colonies are on the decline because of changes in the availability of sand eels, the puffin's preferred fish. Overfishing and warmer water temperatures brought about by climate change are thought to cause the sand eels to move away.

The fish, however, have remained abundant around the Farne Islands and last year they enjoyed a bumper year. “Puffin breeding is becoming increasingly important on the Farne Islands because of the problems they are facing in the northern isles. We are becoming a big player, we are bucking the trend,” said Mr Steel. “I think there could eventually be 150,000 pairs here as long as there's enough food for them.”

The islands are ideal for the birds because of the absence of predators such as foxes and rats, and little disturbance by people. Mr Steel, who lives on the islands, added: “This is a wonderful place. It's beautiful. I've been a bird-watcher all my life and it doesn't get better than being here.”

Farne file

— The oldest puffin recorded on the Farne Islands is 31. About 45 per cent of puffin young on the islands died last year when rain flooded the burrows

— There are 16 islands at high tide, 30 at low tide

— St Cuthbert lived on Inner Farne before he was Bishop of Lindisfarne

— Grace Darling became a heroine in 1838 when she and her father rowed out to rescue five survivors of a shipwreck off the Farnes

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