More than 125,000 birds have been ringed at Wicken Fen National Nature Reserve since 1968 – and some have been recorded as far away as South Africa, Russia and Mali.

To celebrate their 50th anniversary, which takes place on Friday April 27, The Wicken Fen Bird Ringing Group carried out a study of the bird population at the local nature reserve.

The first bird ringed was a Sedge Warbler at 4pm on 27 April 1968. Since then over 125,000 birds have been ringed.

The figures reveal increases in the population of sparrow hawk, collared dove, green woodpecker, great spotted woodpecker, whitethroat, blackcap, chiffchaff, chaffinch, goldfinch and long-tailed tit.

The study however reveals a decline in a number of species including the tree sparrow, song thrush, grasshopper warbler, spotted flycatcher, willow tit, linnet, lesser redpoll and lesser spotted woodpecker.

The decline of these birds at Wicken Fen reflects their reduction in populations across Britain in the past few decades.

Dr Chris Thorne, secretary of The Wicken Fen Bird Ringing Group, was one of the first members 50 years ago.

Around 170 netting sessions are held each year. Netting is undertaken at three sites within Wicken Fen using fine mesh nets which are designed to “pocket” the birds gently without injury.

The birds have a small lightweight ring put around one leg, which has a unique identification number.

When the bird is caught again, either at Wicken or elsewhere, you can learn about the bird’s age, condition and dispersal.

Of the 125,000 birds ringed at Wicken Fen, about 700 have been recorded away from the Fen, 93 of which were overseas, with the furthest being a swallow in South Africa, 9664 km from Wicken Fen (it had been caught by a predatory bird, a fiscal shrike, and a scientist found the ring on the swallow’s body).

Other distant recoveries include a starling in Russia, a marsh harrier in Mauretania and a turtle dove in Mali.

The oldest birds handled include a reed bunting, a reed warbler, a chaffinch and a blackbird, all over nine years since they were first ringed.

A cuckoo ringed and then recaptured almost seven years later, both at Wicken Fen, holds the British “age record” for the species.

The rarest birds ringed have been a great reed warbler in 1971 and a barred warbler in 1979, the only occasions these species have ever been recorded at Wicken Fen. The total number of species ringed is 106.