3 November 2014 Last updated at 04:40
Eider ducks in Northumberland's coastal areas are being harmed by people feeding them fish and chips, a wildlife expert has warned.
Chris Watson says people living or visiting the area often wrongly believe eiders are tame as they are "friendly".
He told BBC Radio Four's Broadcasting House the sea birds may seem to enjoy the food but it damages their eggs.
The Northumberland coast is recognised as a haven for wild birds, including colonies of eiders.
Mr Watson, whose work as a nature sound recordist includes documentaries with Sir David Attenborough, said: "Normally eider ducks eat shellfish not fish and chips - [which is] lacking calcium so the eggs are failing.
"There's a problem because they are such attractive, friendly birds to feed, and yet the food that we are giving them - bread and things like that - is actually causing a dietary problem."
The RSPB says eiders are the UK's heaviest ducks and the fastest flying. As well as the Northumberland coast, they are resident off Scotland and Northern Ireland.