The RSPB is urging farmers, birdwatchers and walkers across East Anglia to keep a lookout for the nation's rarest breeding bird of prey, after launching a hotline to record their sightings.

In 2014, only eight pairs of Montagu's harriers are known to have nested in the UK and the conservation charity said it is essential that the number of breeding attempts made this year are identified and protected from accidental damage, disturbance or persecution.

The RSPB was recently able to locate the birds' African wintering grounds in Senegal, from the migration data provided by an adult male that was tagged last summer in south west England.

Mark Thomas, who leads the RSPB's Montagu's harrier conservation work, said: 'For the first time we know exactly where these rare birds of prey go once they leave the UK.

'Now that these birds of prey have survived the journey back to the UK, it is vitally important that we can identify as many nesting spots as possible.'

Montagu's harrier usually arrive in the UK around May to nest, before returning to Africa in August. It is possible to spot the birds of prey en route, particularly on the eastern and southern coasts of England.

Mr Thomas said: 'The UK population is currently teetering on the brink and we are determined to find out why. Farmers and birdwatchers can really help with the conservation of this threatened species. Now is the best time to witness the adults' airborne courtship before they establish their crop nests and become difficult to spot. If you are fortunate enough to see these breathtaking birds then please contact the hotline to let us know.'

Montagu's harriers are larger than a kestrel, with long wings and a long tail giving them a slender appearance. The males are plain grey, with black wingtips and a white underside. The females are mottled brown with a white rump.

They breed in the east of England on lowland farmland, particularly winter cereals, oilseed rape and field silage.

Any possible sightings of Montagu's harrier can be reported to the hotline on 01767 693398 or emailed to wildlife@rspb.org.uk. Details should include the date, six-digit grid reference if possible, and a contact telephone number. All reports will be treated in confidence.