A PRISON officer caught with a collection of rare and illegal birds' eggs has changed his plea and admitted 11 charges of unlawful possession.

Keith Liddell, from Inverness, had denied 13 charges under the Control of Trade in Endangered Species Regulations 1997 relating to the illegal trade of birds' eggs.

At the end of the second week of the trial yesterday he pled guilty to 11 of these charges.

He had also denied three charges of being in unlawful possession of eggs contrary to the Wildlife and Countryside Act. But pleas of guilty to two of these charges were tendered by his defence solicitor Pauline Chapman.

The trial, which involved more than 190 Crown productions taking up much of the space available in the main courtroom, began last October but was adjourned and resumed this week.

The case was adjourned again on Thursday because Liddell felt unwell. However, when it resumed yesterday the defence submitted pleas of guilty to the majority of the charges.

Liddell, 53, was prosecuted after a raid on his home on June 24, 2009, in which a collection of 2307 birds' eggs was discovered. The collection included eggs from rare birds such as ospreys, peregrine falcons, black-throated divers, and Slavonian and black-necked grebes among many other rare breeds.

Fiscal Kate Fleming from the wildlife crime unit yesterday told the court there were only about 25 breeding pairs of Slavonian grebes in the UK and they were in Inverness-shire.

The charges, she said, did not involve the exchange of money or Liddell being engaged in physically taking eggs from nests. The case was about swapping eggs with collectors in the UK and elsewhere.

Sheriff Gordon Fleetwood deferred sentence until April 9 and told Liddell all sentencing options remained open.

RSPB senior investigating officer Guy Shorrock said in his 20 years' experience it was the largest case of trading in eggs he had dealt with.

Ian Thomson, head of investigations at RSPB Scotland said: "This is among the biggest egg trading investigation that RSPB has ever been involved with. The illegal and outdated practice of egg collecting can have a devastating impact on the future population of vulnerable or slow-breeding species, such as birds of prey and divers."

The outcome of the case follows an investigation which started in 2009 when a County Durham man was convicted of similar offences.

After examining thousands of emails and other material seized from that case, police and the RSPB discovered and exposed a network of individuals involved in trading birds' eggs via the internet. The practice was uncovered as far afield as the US and Scandinavia.

As part of this initial inquiry, investigators were alerted to the activities of Liddell.