An Exmoor bird of prey is to receive extra protection in an attempt to safeguard its nest sites.
Extra vigilance is required, says the RSPB
Merlin numbers on Exmoor, thought to be the only place in the region where they breed, will also be surveyed.
The RSPB says at least one pair of the tiny falcons failed to produce any young last year, due to the effects of human interference.
All wild birds are protected under the law. The RSPB says extra patrols will now be undertaken.
Anyone found guilty of "intentionally or recklessly" interfering with a merlin nest faces a fine of up to £5,000 and/or six months in prison, says the RPSB.
Pc Roger Jolliffe said: "We're doing all we can to protect merlins because it's thought to be the most important site for the birds in southern England and we believe they are under threat."
Helen Booker, from the RSPB, said: "The aim of the survey is to determine the number of breeding pairs across the moor.
"In the early 90s, monitoring of Exmoor showed there were five breeding pairs, but by the time the last survey was carried out in 2000 it had fallen to just two pairs."