Record numbers of two of the rarest British birds of prey have been baffling bird watchers at Lakenheath Fen.
On Sunday 29 marsh harriers and seven hen harriers (pictured here by Andy Hay, RSPB images)were seen at the RSPB reserve on the edge of Lakenheath but nobody is sure why they have turned up in such numbers.
Reserve information officer David White said: “Marsh harriers used to be summer visitors only and though more and more spend the winter here, 29 is unprecedented.
“Hen harriers breed on moorland, mainly in Scotland. In England they’re hanging on by a thread. The highest official record for them here is seven birds.”
The RSPB describes hen harriers as Britain’s most persecuted bird of prey. They are considered particularly unwelcome on grouse moors where they are often found illegally shot or poisoned.
Only about 360 pairs of marsh harriers nest in Britain, but last year 21 pairs nested in the ideal conditions of Lakenheath Fen, of which 18 were successful producing 42 young.
Even so, David believes both species are coming here from further north.
But he added: “There doesn’t seem to be much evidence of a hard winter further north. There have been times when the weather in Scandinavia has been hard and we’ve had all sorts of things turn up, but not this year.
“There is plenty of habitat for them here — it’s a 300 hectare reserve.”
He said the hen harriers appear to be hunting over the surrounding countryside during the day, returning to the reserve to roost.
“The best place to see them in the reserve is the Joist Fen viewpoint any time from about 2.30pm onwards,” he said. “It’s very much an evening thing, because they fly around the reserve where in the mornings they just fly off.”
Marsh harriers are believed to have a 10km hunting range but are often seen on the reserve.
Visitors on Sunday not only saw the harriers but also saw two of the reserve’s rare cranes and an otter.
A number of Lakenheath-born marsh harriers have been given coloured and numbered wing tags in an effort to see where they go.
If you spot a marsh harrier locally with a wing tage, and can record its number, the reserve would like to know where and when you saw it.
You can contact the reserve on 01842 863400 or at firstname.lastname@example.org