A retired solicitor from Devon who amassed a collection of hundreds of eggs over nearly 70 years has been fined almost £5,000 and had his haul confiscated.

William Beaton, 73, told Plymouth magistrates he took his first egg – from a blackbird’s nest – on a “fine April evening” when he was five.

He claimed he had collected out of interest rather than for profit, but the wildlife charity the RSPB expressed concern that he had targeted some rare species.

Beaton admitted taking eggs from birds including barn owls, little terns, cirl buntings, red throated divers and avocets.

Earlier this year he was fined £4,000 in Scotland after being caught with eggs from the great skua and the rock dove.

Beaton took his first egg in 1948. He carried on even though his hobby became illegal in 1954. Since the 1981 Wildlife and Countryside Act was introduced it has also been against the law to possess an egg from any British wild bird.

In a statement read out to the court, Beaton, of Yelverton, Devon, said: “I’m guilty of collecting wild birds’ eggs and having a collection of the same. I am sorry for that but there are collectors and collectors … I am not the worst of the worst or the baddest of the bad.

“The number of eggs in my collection may seem like a lot but it was built up over a number of decades. I’m glad I have been caught – it will enable me to appreciate the seriousness of what I have done.”

Gareth Warden, for the prosecution, said police searched Beaton’s home in June. Two chests of drawers containing birds eggs were seized along with diaries and books relating to taking eggs. More than 500 eggs were found.

Warden said the investigation in England began after Beaton was caught in Scotland.

The magistrate Lin Martin imposed a fine of £4,705 and told Beaton: “We have taken into account the remorse you have shown … We do not want to see you back in court.”

In a statement after the case, the RSPB said: “Mr Beaton had shown a worrying trend of targeting rarer species in recent years. We hope this prosecution will stop him from reoffending and send a message out to others.”

The eggs will be put in a museum.