An investigation is continuing into a disease at one of Britain's largest heronries, which is causing the legs and wings of heron chicks to snap as if they have rickets. Scientists fear that the poison that is causing serious deformities in the chicks could have the same effect on the human population.
The disease at Besthorpe nature reserve, in Nottinghamshire, killed 22% of chicks this year before they left the nest because their wings became so deformed they were unable to fly. The chicks have either starved in the nest or tried to take off then plunged to their deaths.
X-rays showed other birds found dead but which had been apparently healthy, had broken wing bones. After blood tests the government's central science laboratory has established that the the chicks' bodies contained PCBs and dioxins - both banned substances. The greater the concentration of the poisons the worse condition the chicks were in and the two substances appeared to have prevented the bones forming properly. The science report said: "Work at the Institute of Zoology has shown weaknesses in the long bones of the heron chicks that are consistent with low mineralisation of growing bones, a syndrome similar to rickets."
John Black, from the Nottingham Wildlife Trust, who rings herons as part of a long running scheme to keep track of numbers and ages of the birds, said that the deformities in the heron chicks were first recorded in 1996. Adrian Blackburn, of the North Nottinghamshire ringing group, who climbs up to the 38 nests in the heronry to ring the chicks, noticed that some were suffering broken bones. It has taken nine years for the ornithologists to get sufficient funding and backing to find out what was happening to the herons, which in some years appeared to rear nearly all chicks successfully but in others, like this year, lost a quarter of all the young."
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