After 21 years of breeding there, the RSPB site believes this could be a bumper time for the rare bird of prey.

The first young bird was spotted flying from the nest on Monday, June 30.

10 facts about marsh harriers,

a.. Marsh harriers are medium-sized, slender hawks, the female being considerably larger than the male. They are characterised by long, narrow, rounded tails, small beaks and long, slender legs. The most notable characteristic is the owl-like ruffs of facial feathers that cover unusually large ear openings - an adaptation not for low-light hunting, but to locate prey by its rustling and squeaking in tall grasses.

b.. The largest UK breeding populations are on the Norfolk and Lincolnshire Wash, the North Norfolk coast and the Isle of Sheppey in Kent.

c.. Marsh Harriers can be seen easily at a number of nature reserves, including the RSPB sites at Elmley, Kent; Leighton Moss, Lancashire; Minsmere, Suffolk; Titchwell Marsh and Strumpshaw Fen, Norfolk; Ouse and Nene Washes, Cambs, and Blacktoft Sands, Yorkshire.

d.. The bird is widespread elsewhere in Europe with an estimated 93,000-140,000 breeding females. It is also found across Asia and south into Africa.

e.. Most British marsh harriers migrate to western Africa for the winter although at least 100 stay all year, particularly in north Kent and the Norfolk Broads, where birds gather in impressive roosts.

f.. The name harrier comes from the Old English word hergian, which means to harrass by hostile attack

g.. Marsh harriers feed on small birds and mammals, reptiles, fish and invertebrates.

h.. Courtship is spectacular with male birds looping the loop and spinning through 360 degrees as they tumble from hundreds of feet up. Males release food in mid-flight with females turning upside down to catch it in their talons.

i.. They lay between three and six eggs in nests hidden in dense reedbeds or crops such as wheat and oil seed rape.

j.. They live for up to 15 years although 75 per cent of young birds die within three years.

k.. Marsh harriers were heavily persecuted from the 18th century onwards and are still regularly shot as they migrate over southern Europe, particularly Malta and Cyprus. Although they are strictly protected in the UK, nests are still destroyed either deliberately or by accidental disturbance.