Heron ringing reveals chick deformity puzzle
Heron ringing reveals chick deformity puzzle
Each year up to 700 grey heron chicks are ringed
in Britain by conservation groups in their quest
for research and to monitor trends.
Recently, however, their studies
uncovered an unexpected
problem as
Michael Edwards
reports
THE North Nottingham Ringing Group were alarmed to find nine chicks with deformities of the long bones in the wings and legs, something that they had never come across previously.
English Nature agreed to issue a licence to cull any deformed chicks. Dr James Kirkwood, then at the Zoological Society at London, undertook the post-mortems, which pointed to a serious calcium deficiency, suggesting either poor calcium in the diet or that the chicks had suddenly started to metabolise previously laid down calcium.
It was assumed that this was a one-off incident. But the following year, nine more chicks out of 24 were found to be deformed. Similar problems with herons in a Yorkshire colony have also been discovered.
"This confirmed that they had a serious dietary problem and calcium deficiency," said Mr Nigel Clark of the British Trust for Ornithology (BTO). "There appeared to be no obvious suggestion as to what could be causing the deformities."
Since agricultural pesticide poisoning was a possibility, MAFF were contacted who considered it as a potential "incident". On further ringing trips, more deformed chicks were collected for analysis and by the end of the season it became clear that there was no evidence of high levels of agricultural pesticides.
But another anomalous result also showed up. Many of these chicks had extremely high levels of selenium, a rare metal that is known to cause problems in poultry, livestock and wild ducks in the USA.
If you have related information that might be useful or require information about crippled herons, please call Nigel Clark at BTO on 01842 750050.