Is it a chicken or a turkey? No, it's a churkey

Its naked neck has long ruffled feathers among both scientists and poultry fanciers.

Is it there because this fowl is a hybrid of a turkey and a chicken? Many once mistakenly believed that to be true, with the result the bird is sometimes still called a 'turken'.

In fact, the Transylvanian Naked Neck, to use its proper name, is a chicken.

But the reason for its mysterious bald patch has continued to intrigue, with home-spun theories abounding.

Some like to think it is Mother Nature's way of giving us something easier to pluck than the average bird. Others have archly speculated (bearing in mind the province the bird is named after) it is to give vampires easier access.

Now, at last, the heated debate over its curious appearance can cease. For a DNA study by scientists at a British university has discovered the bird developed its distinctive look to stay cool.

Dr Denis Headon, who led the research at the Roslin Institute at the University of Edinburgh, said the findings could help breeders produce chickens more suited to hot countries.

'Naked neck chickens have no feathers whatsoever on their necks, and if you were to pluck one you'd discover fewer feathers on their bodies as well,' he said.

'But they behave like normal chickens, they do lay good eggs and are also very popular for their meat. They are, however, more resistant to heat than normal chickens.'

Transylvanian naked necks originated in Central Europe and were introduced to Britain in the 1920s.

The study found that their naked neck is the result of a random genetic mutation that causes the overproduction of a feather-blocking molecule called BMP12.

The mutation first arose in domestic chickens in northern Romania hundreds of years ago, making them look like they have head of a turkey on a chicken's body with a long, deep-red neck in between.

Dr Headon said that when the scientists treated standard-breed chicken embryos with BMP12 in the lab, the young chickens developed no feathers on their necks, suggesting the neck is more sensitive to the molecule.

He and his team then did a further DNA test which revealed an acid derived from Vitamin A is produced on the Transylvanian Naked Neck's skin. This acid enhances BMP12's effects thus making the birds' necks bare, they found.

Genetic mutations are usually bad for an animal. But in this case it has helped the bird prosper because their resistance to heat has made them popular with poultry farmers in hot countries such as Mexico where they can produce better eggs and meat than other breeds.

It is likely ostriches and storks lost their neck feathers to stay cool too, but it is unclear whether BMP12 played any role. For vultures, the absence of neck feathers helps them to poke about the insides of carrion unimpeded.

'Evolution has always found it easy to loose neck feathers wherever it gest hot and the bird gets big,' said Dr Headon.