The early run-offs are one of many signs of warming temperatures that have caught the attention of hunters and anglers around the United States -- an influential group that has its pulse on the outdoors.

"If you have early runoffs then you have less water in the summer and autumn," said Oregon-based Jack Williams, a senior scientist with conservation group Trout Unlimited.

Trout like cold water and become stressed on hot summer days, because water levels are lower and temperatures are higher than would have been the case if the run-off came at more traditional times from April to June.

"We are finding a lot of concern among anglers and hunters about climate change. These people value traditions and their family and it will affect their children and their ability to enjoy these kinds of outdoor experience," Williams said.

The political run-off could flow as far as the Republican Party, which has broad support from hunters and anglers but which has been reluctant to address global warming.

President George W. Bush and Vice President Dick Cheney both hunt and fish. But both also have ties to the oil industry and they have been less than enthusiastic about embracing political measures to curb greenhouse gas emissions.

The vast majority of scientists agree that human activities such as burning fossil fuels are contributing to a rapid warming of the planet that cannot be explained by natural cycles.

WHERE ARE THE GEESE?

Professional hunters have also detected climate-related changes that affect their trade.

"The past season was a bad one for goose hunting ... I would say the clients only got about 40 percent of what they usually get," said Corey Marchbank, a goose hunting guide in the eastern Canadian province of Prince Edward Island.

He said the weather seemed to be the main factor. Mild autumn and winter temperatures meant the geese could stay longer in coastal areas that used to freeze up.

An early grain harvest last season also meant there was less in the fields to attract the birds when the hunting season began in October.

Hunters and anglers notice such things and are behind many conservation measures in the United States, not least because they could not shoot game or catch fish without protected habitat.

"We have a lot of support from duck hunters who know our work in protecting wetlands is vital," said Ben McNitt, communications director for the National Wildlife Federation.

Outdoorsmen were seen as instrumental in getting congressional protection from oil and gas drilling last year for two wild areas: the Valle Vidal in New Mexico and the Rocky Mountain Front in Montana.

"Sportsmen played a critical role in convincing Congress to protect these areas," said Kira Finkler, legislative director for Trout Unlimited.

Groups like Trout Unlimited are now directing political attention to climate change issues and policy.

A commonly cited figure used by the National Wildlife Federation is that more than 40 million Americans hunt and fish and that they spend US$70 billion a year on such activities.

Guns, guides, gas, rods, licenses: it all costs money. And the numbers and the cash all add up to influence.

A nationwide survey of licensed hunters and anglers last year commissioned by the National Wildlife Federation found that 76 percent of those polled agreed that global warming was occurring and the same percentage said they had observed climatic changes in the areas where they lived.

Eighty percent of the outdoors-types surveyed said they believed the United States should be a world leader in addressing global warming.

Half of those polled identified themselves as evangelical Christians -- a key support base for the Republican Party, which has been divided on the issue of global warming.

"If the priorities of evangelicals change from social issues like abortion to the environment it could have a profound effect on the Republican Party," said John Green, a political scientist at the University of Akron.