Recoveries of ringed birds indicate great longevity in species such as the fulmar, gannet, manx shearwater and storm petrel, said Chris Mead, of the British Trust for Ornithology (BTO).
Fulmars have already been shown to live to more than 40 years, and gannets to 36. But because of their slow breeding rate, some fulmars in old colonies, such as St Kilda off the Scottish coast, may have chalked up a century.
There is no proof yet because leg-rings strong enough to last that long have only been in use for 30 years. But, Mr Mead said: "If I had to lay odds, I'd say it would be very unlikely there wasn't a 100-year-old fulmar, or a few of them, in the St Kilda colony, and I wouldn't be at all surprised if it was the same for the gannet."
The BTO's latest five-year report on the recovery of ringed birds shows a number oflongevity records for waders and seabirds, including 18 years for the ringed plover, 26 for the bar-tailed godwit and 33 for the common tern - all proved from recoveries made in 1996. In the five years to 1998, storm petrels have been shown to live to at least 32 years, Manx shearwaters to 35, gannets to 36 and fulmars to nearly 41.
All are of the pelagic species - birds which range far out to sea - and all are extremely slow breeders, not laying until they are seven or eight years old, and then only a single egg. "If they did not survive a long time, they would die out," Mr Mead said.
"I'm certain that quite a lot of fulmars are over 50. About 8 per cent, or less, die per year, so it is quite likely, provided there is no senility, that in a colony of 100,000 birds - as in St Kilda - a handful would live to be 100."