Towards the end of our interview, Bryan Nelson reflects that if he had been starting out on his research now, his life would have been very different.

The world's greatest authority on the Atlantic gannet and an expert on pelicaniformes (a group of water birds), Nelson, now 81, lived for years on islands as diverse as Bass Rock and the Galapagos, always accompanied by his wife and research collaborator June. Living on a shoestring, camping and fired by the spirit of adventure, he and June simply wouldn't be allowed to live like that now, he notes.

"The world was very different in 1960," he says, framed against a view of the Solway Firth in the conservatory of his Galloway cottage. "It was simpler; it was slower; it was less technological and there were fewer irritating bylaws, restrictions, rules and regulations. Everybody when they get old thinks the old days were better, but in many ways they were."

Nelson's recently published book, On The Rocks, the beautifully illustrated plain-speaking memoir of a life spent researching sea birds all over the world, is testament to the optimistic, free-thinking "lets-give-it-a-go" philosophy that pre-dated the risk-averse health and safety culture.

"We were nearly penniless, without home, job or possessions, but the future seemed wonderful," he writes of the year he and June spent as the only humans on two Galapagos islands in 1964. Living without clothes in the heat of the equatorial sun, watching manta rays and sharks, dancing on the sand to "fuzzy music from Radio Belize" and latterly sharing their beach with sea lions, their lives were governed by natural forces.

As part of the superficially idyllic tropical island lifestyle, however, they lived in "squalor" in a small tent and had no means of summoning help from other islands. A fall on the "needle sharp" lava formations could have proved nasty and dangerous. Calculated risk was part of life for them both there and on Bass Rock, where Nelson climbed down sheer cliffs to check nests without the safety equipment that would be obligatory today – but it all turned out fine. The couple assumed that "if you're fit-ish, you'll be all right", and they were.

Nelson takes pride in this, but also recognises he and June were fortunate. It was easier to take risks then and besides, studying animal behaviour was in vogue, unlike today. "If I had to start again today, I just wouldn't have a hope," he says with a shrug. "A lot depends on luck and I've really just been very lucky."

Nelson was born in the West Riding of Yorkshire in 1932, going to school in Saltaire. His father was an engineer, though had no formal training. Nelson's love of birds began during the war, when he was given a bird book. "From the age of 11, I was mad on birds and in fact I learnt all the songs and calls of the common British birds, which has been immensely useful."

While Nelson first studied birds in the Yorkshire Dales, he has been based in Scotland as an adult, studying zoology at St Andrews University before a PhD in Oxford and starting out as a researcher ringing gannet chicks on Ailsa Craig. He spent most of his career on staff at Aberdeen University and is best known for what he has revealed about the life of the Atlantic gannet. The Nelsons spent four years in total on windswept, inhospitable Bass Rock in the Firth of Forth studying the birds' ecology and social behaviour.

No-one lives on the island now, but between 1960 and 1963, the Nelsons shared it with lighthouse keepers, though they themselves lived for most of the time in a draughty hut within the walls of a ruined chapel, from February to November. So just how cold did it get?

June throws back her head and laughs. "Very," says Bryan with feeling, as we share a lunch of herrings and ham in their cottage dining room, surrounded by books and paintings of birds.

"In those days, the sleeping bags were absolutely pathetic," interjects June.

"We had a paraffin oven and a stove, and so in a 12ft by 8ft hut, you could build up a little fug with those," says Bryan, thoughtfully. "But we didn't have any insulation. We should have had."

They loved the simplicity of life there, even when they found 141 earwigs in their chip pan.

The couple dug out a plunge pool near the chapel, taking out masses of rubble and slick mud, only for it to fill with "deep yellow" seepage water. "Still it was a pool," writes Nelson, "and had you chanced unexpectedly on the scene on many a summer's day you might have wondered at the sight of Adam and Eve leaping blithely into this sinister hole".

Pictures of the Nelsons from the time reveal a handsome couple, Bryan a tall, long-limbed young man with a shock of blond hair and June a smiling, dark-haired beauty. They met in 1954 at Spurn Point bird observatory on the Humber estuary and married six years later. In his book, Nelson remarks they never argued in spite of living solely in each other's company for months. What, never? Nelson raises his eyebrows. "It's absolutely true, we did not have an argument for the first seven years and that's after six years of courtship, so that's 13 years," he says, with a shrug.

He attributes this astonishing harmony to the fact of being so absorbed by the work but June adds that it is also due to their complementary personalities. "I am not by nature gregarious," admits Nelson, unlike his outgoing wife.

After three years on the Bass, the couple took off on their own meagre resources to study the booby and the frigate-bird on the Galapagos. The only high-level assistance they had while there came unexpectedly from the Duke of Edinburgh who came ashore one day from the royal yacht Britannia and agreed to transport their many notebooks back to Britain. The Nelsons were invited to lunch on the yacht, Nelson recalling he went aboard barefoot and "in patched shorts liberally splattered with albatross vomit", not that HRH seemed to care.

A year after returning to the UK and moving to Aberdeenshire, Nelson accepted a year-long research fellowship on Christmas Island in the Indian Ocean. When the couple arrived, they found the future of the rare Abbott's booby – whose only nesting place was on the island – hung in the balance as its prime habitat lay directly on top of phosphate deposits that were due to be mined. The birds suffered a terrible decline as a result of the mining and in 1974, Nelson went back to find much of their habitat destroyed.

He gave evidence to a government committee in Canberra (Christmas Island being a territory of Australia) and that helped start an international outcry, which led to Christmas Island being made into a National Park, giving the Abbott's booby much-needed protection. Nelson identifies this as his most proud achievement.

In 1968, he and June went to Jordan to set up a project for the study of migrant birds on a desert oasis and when they returned home in 1969, Nelson took up a lectureship at Aberdeen University.

Five years later, the couple had twins, Simon and Becky, and in 1978 the whole family went to Cape Kidnappers in New Zealand for six months to study gannets, before returning once again to Scotland.

Throughout his career, Nelson has maintained a deep interest in the gannet. His work on the birds is renowned and he counts Sir David Attenborough among his admirers, though the two have never met. "They are just hugely spectacular birds – huge wingspan, deep diving – and their social life is complex. There is no hierarchy. There is just ownership of territory. Also they have this unique ability to forage big distances from base – 400 miles – and to handle large prey."

Gannets have started to thrive since systematic persecution came to an end, but there are signs they are now under pressure because the population has expanded so much. "A bigger proportion are coming back to the colony, re-pairing with the same mate, holding the same site, but just not breeding, and that's very interesting because that percentage is going up."

He is less worried about natural fluctuations in population, however, than in ones caused by man. On this subject his outlook is bleak.

"I just feel that man has done an absolutely vast amount of damage to the world and to its wildlife," he says, clearly irritated by it. "I think the population is far too huge, far too exploitative, the developed part of the world far too demanding of its standards and far too wasteful. It's part of the syndrome that 90-odd percent of human beings feel no sense of responsibility towards the environment or other organisms. Whatever you do in terms of exploitation, so long as it's economically valuable, that's OK. It's just an appalling attitude."

He frowns and raises his hands in exasperation. Is he depressed by it all? "There's no point in being depressed," he insists. "The point is to do something about it."