Changes to farming practices in the UK are not the cause of a crash in Bewick’s swan numbers, research suggests.
Numbers of the swans, which overwinter in the UK and migrate north to Russia for the summer to breed, fell by nearly 40% between 1995 and 2010, the Wildfowl and Wetlands Trust (WWT) said.
The birds largely feed in farmers’ fields during the winter in the UK, raising concerns that intensification and mechanisation of farming was preventing them getting enough food.
The study, published in the journal European Journal of Wildlife Research, found no connection between body condition and the recent declines, and the falling numbers were unlikely to be due to food shortages.
The conservation organisation is continuing to work with partners throughout the Bewick’s swans’ migratory range to research all the possible reasons for the declines, including illegal hunting, poisoning, collisions and habitat loss.
WWT principal research Officer, Dr Kevin Wood, said: “Bewick’s swans have to leave the UK in peak condition to survive their gruelling migration to Russia and arrive ready to breed and rear cygnets during the brief Arctic summer.
“Although the British countryside has changed considerably over the last half century, there’s no evidence that the swans are anything other than well fed while they’re here.
“It’s good news, and we’ve eliminated one line of enquiry, which will allow us to now focus on other issues that might be affecting the swans.
“Hundreds of WWT staff and volunteers have helped to catch and measure swans over the last five decades, so it’s great to be able to use the data to help examine the issues that the Bewick’s swans might face.”