The RSPB has told worried birdwatchers to call the police to report nature crimes after a council delayed the removal of netting over the nests of migrating sand martins, which had flown thousands of miles to nest and lay eggs.

Wildlife activists reported seeing a kestrel become entangled in the wide holes of the netting covering over a kilometre of the cliff at Bacton beach, north Norfolk.

The netting was put in place to deter birds from nesting as part of an anti-erosion scheme to protect a local gas terminal.

Locals say that winds caused parts of the material to fall down overnight, meaning some sand martins managed to get to their nests.

The RSPB said that if reports are accurate, this means the council and contractors could be committing a wildlife crime, as disturbing a live nest is illegal under the 1981 Wildlife and Countryside Act.

A spokesperson for the local RSPB said: "All wild birds whilst they are nesting are protected by the countryside act so if they are being disturbed that is an offence and we would recommend the witness calls the police.

"If contractors are aware of birds being caught and are not taking action, that is a crime.