The grouse hunting season began on 12 August

As the Glorious Twelfth marked the start of the traditional shooting season on Tuesday, many expected record numbers of birds due to warm weather.

But some experts believe pickings could be slim as thirsty birds desert traditional moorland and head for water.

Police have been on the alert following warnings from animal rights protestors that some shoots may be disrupted.

But one expert claims the continued dry spell may possibly scupper some hunters' chances of finding their prey.

Adam Smith, of the Game Conservancy Trust, said that while some parts of the country may have their best season in years, others may suffer due to the heat.

He said: "I would have been more bullish a few weeks ago.

"Some areas are talking about having record shooting.

"But there are other areas where the lovely weather might have been too good, the hills are becoming very dry and they are beginning to run out of water.

"Even if it doesn't reduce the number of grouse, it will make them harder to find.

The heatwave may have driven grouse to look for water

"It should be a good year - if the guys can find where the birds have gone."

Dr Colin Shedden, Scottish director of the British Association for Shooting and Conservation, agreed that the recent weather may have been "too dry" for the birds - but predicted it could be the best season in a decade.

He said: "The general indications are that a mild winter and a good spring has led to a good grouse breeding season.

"We are reasonably confident that it can prove to be one of the best years for grouse for the last five, or maybe even 10 years."

Last month experts said soaring temperatures had boosted numbers of the rare red grouse across the north of England.

Numbers are up by an average of 25% on 2002, according to new figures.

Durham and Northumberland are doing especially well, according to the Moorland Association.

Numbers are also up in Cumbria and the North Yorkshire Dales.