Farne seal pups tracked by coloured coats

But mothers will continue to give birth for another month, with the peak occurring in around 10 days.

Last year the total of newborns for the Farne Islands was 1,318. But the average mortality rate is 50-55%.

"The main threat is storms in which the youngsters are washed off the rocks in the first few weeks of their lives and they drown," said David Steel, the National Trust's head warden on the islands. "But so far this year the weather has been quite kind to the young seals."

The wardens visit the colony every three days or so and mark batches of pups with a different colour on every outing.

This allows them to monitor survival rates of different groups of youngsters.

They also radio tag some pups to follow their movements in the first year of their lives, after which the device will be lost as the animals moult.

The programme has shown that young seals from the Farne Islands will travel to other colonies in Lincolnshire and the Firth of Forth in Scotland.

Others have turned up in the Orkneys, Shetland and Faroe Islands, and even as far afield as Norway.

"One bull which was marked on the Farne Islands in 1981 is still around," said David.