Rare black grouse found in areas including North Yorkshire have had a record-breaking breeding season thanks to the warm, dry conditions in June, experts have said.

The annual breeding count of the bird in England has revealed that each hen has produced more than four chicks on average, almost four times the numbers of young reared in previous years.

Most hens managed to rear chicks and some were spotted with ten or 11 young, which is “quite exceptional” for black grouse, according to Dr Phil Warren, a specialist in the species with the Game and Wildlife Conservation Trust.

“This is all in stark contrast to last year when breeding productivity was appalling and one sample of 35 hens only raised seven chicks between them.”

The difference was down to the weather conditions in June when the chicks hatch, he said.

“Last year it was cold and wet and this year it has been warm and dry. Warm dry conditions mean an abundance of insects such as sawfly larvae which young chicks depend on when they first hatch.”

He added: "This bumper breeding is extremely encouraging and we expect to see this reflected in an increase in males attending leks next spring."

Black grouse were once common in most of southern England, from Dartmoor to Norfolk, but are now found only in four upland areas in Northumberland, County Durham, Cumbria and North Yorkshire.

Numbers of the red-listed bird have declined from around 25,000 displaying males in 1970, as a result of a number of threats including habitat loss and increasingly intensive agriculture.

Populations dropped to their lowest recorded levels following two extremely wet summers and the hardest winter for more than 30 years in 2009/2010, but this good breeding year is a much-needed boost for the species.

The higher numbers also mean conservationists can work to increase the bird's range in the Yorkshire Dales by moving young males in the core of the range to specially selected release areas.

The count, which has been conducted annually for 25 years, found record breeding productivity this year, with an average of 4.4 chicks per hen, up from the average 1.2 chicks per hen in previous years.

Dr Warren said that in England 95% of remaining black grouse were found in areas associated with grouse moors, which are managed for red grouse shoots.

Measures to keep down predators and improve habitat have helped black grouse survive and enabled them to take advantage of this year's good weather conditions, he said.