Lee McLaren, 35, and Jamie MacLaren, 34, face up to two years in jail if they are unable to pay the penalty.
The fines, handed down by Bill Wright, the honorary sheriff, at Kirkwall Sheriff Court, delighted Royal Society for the Protection of Birds officials. They said the severity of the sentence could play a key role in helping to stamp out egg collecting.
Keith Adam, the procurator fiscal, said the brothers were spotted by RSPB site manager Keith Fairclough while they were acting suspiciously on one of the society's Orkney reserves. He alerted police wildlife liaison officer Dave Dawson.
PC Dawson found a collection of wild birds' eggs at the brothers' rented caravan.
The court heard that they had targeted hen harrier, merlin and red throated divers - all given special protection under the Wildlife and Countryside Act.
They also had eggs illegally collected from the nests of curlew, fulmar, dunlin and a starling. Of the 31 eggs found, 17 were from the schedule one of specially protected birds.
Mr Adam said: "There has been a considerable drop in the hen harrier population in Orkney and that is not assisted by them taking these items.
"There are less than 120 pairs of red throated divers in Orkney and less than 20 pairs of merlin - so clearly taking eggs like this is to be discouraged."
The brothers, both of Portsmouth, admitted 70 charges under the Wildlife and Countryside Act, including taking and possessing eggs and disturbing rare and protected birds.
They have four weeks to make arrangements to pay the fines. If they cannot raise the money the alternative penalty is up to two years in jail. Jamie MacLaren, a labourer, earns pounds 120 a week, and his brother earns pounds 53 a week as a part-time taxi driver.
The previous highest fine handed down to an egg collector was pounds 16,000 later reduced to pounds 2,000 on appeal.Reuse content