Nature-lovers feeding leftovers from Christmas dinner to the birds could be unwittingly endangering the lives of the wildlife in their garden.

While many festive foods can make ideal winter treats, the RSPB has warned that cooked turkey fat is extremely dangerous to garden birds and could even kill them.

The charity said many people pour the leftover contents of roasting tins onto bird tables, hoping it will give extra energy and nutrients – but wrongly believing it is as good for birds as other fats like lard and suet.

However, cooked turkey fat is completely unsuitable for birds for several reasons, including:

?It stays soft when cooled, meaning it can smear onto feathers, damaging birds' water-proofing and insulation.

?Salt rubbed liberally into turkey joints to crispen the skin can be toxic to birds in high quantities.

?Meat juices mixed with fats can go rancid very quickly, becoming a breeding ground for food poisoning bacteria.

Erica Howe, from the RSPB in the east of England, said birds are prone to bacterial infections at this time of year when their defences and energy levels are low because of the cold.

'Please, please don't use fat from roasting tins to feed garden birds,' she said. 'It's great that so many people want to try and give birds extra treats but in this case you could be killing them with kindness.

'The cooking juices from all other meats are equally a complete no-no. It's not just turkey fat.

'If you want to use the fat from your Christmas meat, just cut off the fatty bits before cooking. Uncooked fat from any meat is perfectly good bird food and very suitable for making bird cakes.

'With all the fattening things people eat over Christmas, this is an easy way to trim up and help birds survive.'

Many other festive scraps can be safely fed to garden birds. The RSPB recommends Christmas cake, mince pie pastry crumbs and biscuit crumbs. Other suitable foods for birds include mild grated cheese, cooked or uncooked rice, dry porridge oats, cooked potatoes and fruit.

Water companies agree with the RSPB that the best way to dispose of meat fat is to leave it to cool down and put it in the bin, not pour it down the sink.

John Clare from Anglian Water said: 'Sewer blockages caused by fat, oils and grease from cooking are a year-round problem for water companies, but it is made worse at Christmas.

'A turkey big enough to feed six people produces around three quarters of a pint of fat. In the Anglian Water region alone some 250 tonnes of fat from roast turkey dinners is expected to go down customers' drains – the equivalent of nearly a million blocks of butter.

'When people pour fat down the sink it quickly cools in the sewers, sets hard and creates incredibly hard-to-shift blockages. That can mean sewage is forced out into homes and gardens, causing misery at what should be a happy time of year.'