CONSERVATIONISTS trying to restore a breeding population of Osprey to Poole Harbour say they are ‘shocked’ and ‘devastated’ following the deaths of six birds in less than a week.

Five of the birds of prey died suddenly following a suspected nutritional thiamine (vitamin B1) deficiency, while one was found drowned after becoming entangled in thick algae.

Charity Birds of Poole Harbour is currently undertaking the second phase of its Osprey translocation project following the successful release of eight chicks last summer.

The five-year project aims to restore a south coast breeding population of the birds for the first time in over 200 years.

Chicks are being brought down to Poole Harbour annually from Scotland until 2021. This summer the charity received 14 new chicks, with the first birds released on July 31.

Seven of these birds are now exploring the harbour, including Arne and Middlebere, and interacting with several migrant adult Ospreys. However, over a six-day period near the beginning of August, six birds, including four which had yet to be released, died.

When the Birds of Poole Harbour team first noticed signs of illness in some of the birds, they were immediately taken to specialist vets at Cotswold Wildlife Park. However, the birds deteriorated quickly despite injections to boost their thiamine levels. The vitamin is required for basic cellular metabolism and is crucial in the development of young birds and animals.

Pathology tests ruled out a bacterial or viral infection, and experts agreed that a thiamine deficiency was the main contributing factor in the deaths.

“The speed with which the young Ospreys had become ill and died was both shocking and devastating, not least because we are still unsure of what had caused their sudden deaths,” the charity said.

“The protocols we used this year are identical to those used in our successful first year.”

They added: “A project of this scale and ambition will always face challenges – what is important is the manner with which we respond to and learn from such challenges.”

After the loss of five birds to illness, the charity discovered one of the first birds to be released had drowned. Getting caught in dense weed is a danger “all young Ospreys face during their first weeks on the wing”, the charity said.

Although five of the birds were unable to recover from their illness, one which fell ill and initially suffered near paralysis in both legs is now showing signs of improvement after being treated at Cotswold Wildlife Park.

  • Ospreys, which feed exclusively on fish, historically bred across the whole of Britain and north-western Europe, but populations drastically declined in the Middle Ages and became extinct in England by the mid-1800s

  • The bird used to have the local nickname ‘Mullet Hawk’ when it bred in the south of England

  • They are annual visitors to Poole Harbour as they pass through on their northward and southward migrations between their breeding grounds in Scotland and central England and their over-wintering grounds in West Africa