Sea patrols have been increased around a North East island after the theft of several rare bird eggs.
Police found green mooring rope near the scene of the theft
An unknown boat landed on Coquet Island, off Amble, Northumberland, on 10 June and thieves made off with a clutch of Roseate Tern eggs.
The only clue to the incident was a length of green rope tied to a mooring ring next to the nesting terraces.
Roseate Terns are amongst Europe's rarest seabirds and virtually the entire UK population nests at Coquet.
The RSPB has offered £1,000 leading to the arrest and conviction of those responsible.
No landing is allowed on the island, where 91 pairs of Roseate Terns nested in 2005.
Those eggs which remain on the island have been forensically marked and the RSPB has stepped up the number of wardens on the island to provide 24-hour cover, backed by CCTV cameras.
Northumbria Police's Marine Unit officers are also on patrol around the island speaking to anyone using a boat in the area.
Force wildlife officer Pc Paul Henery, said: "We are using everything at our disposal to protect these eggs of this internationally important population of Roseate Terns.
"We will be vigorously targeting the egg collectors who are depriving the public of the pleasure of seeing these magnificent birds."
Roseate Terns are protected by law and anyone found disturbing, killing, injuring or taking the birds, their nests, or eggs can be fined up to £5,000 or face six months imprisonment.