Between 1970 and 1972, a pair of Montagu's harriers, Britain's rarest breeding birds of prey, nested in the reed bed. The RSPB bought the reserve in 1973 for £53,000 (£,000 in 20). The Montagu's harriers did not return, but marsh harriers did, and the RSPB commenced improving the habitat and facilities, including embanking the lagoons and building a car park and visitor centre. Avocets, then still very rare in the UK, first bred here in 1984. The visitor centre facilities were improved between 1987 and 1989 to cope with the numbers of visitors.