"Birds are the quintessential 'canaries in the coal mine' and are already responding to current levels of climate change," said the report, launched at a United Nations conference in Kenya on ways to slow warming.

"Birds now indicate that global warming has set in motion a powerful chain of effects in ecosystems worldwide," WWF said.

"Robust evidence demonstrates that climate change is affecting birds' behaviour -- with some migratory birds even failing to migrate at all."

In the future, it said, unchecked warming could put large numbers of species at risk, with estimates of extinction rates as high as 72 per cent, "depending on the region, climate scenario and potential for birds to shift to new habitats".

It said the "more extreme scenarios" of extinctions could be prevented if tough climate protection targets were enforced and greenhouse gas emissions cut to keep global warming increases to less than 2 degrees C (1.6 F) above pre-industrial levels.

Already in decline in Europe and the United States, many migratory birds were now missing out on vital food stocks that are appearing earlier and earlier due to global warming, widely blamed by scientists on emissions from burning fossil fuels.

In Canada's northern Hudson Bay, the report said, mosquitoes were hatching and reaching peak numbers earlier in the spring, but seabirds breeding there had not adjusted their behaviour.

In the Netherlands, it added, a similar mismatch had led to the decline of up to 90 per cent in some populations of pied flycatchers over the last two decades.

"NOWHERE TO GO"

Predicted rising temperatures could see Europe's Mediterranean coastal wetlands -- critical habitats for migratory birds -- completely destroyed by the 2080s, it said.

Rising temperatures were also seen having disastrous impacts on non-migratory species, as their habitat ranges shifted.

"Many centres of species richness for birds are currently located in protected areas, from which birds may be forced by climatic changes into unprotected zones," the report said.

"Island and mountain birds may simply have nowhere to go."

In the US, unabated warming was seen cutting bird species by nearly a third in the eastern Midwest and Great Lakes, while almost three-quarters of rainforest birds in Australia's northeastern Wet Tropics were at risk of being wiped out.

"In Europe, the endangered Spanish imperial eagle, currently found mainly in natural reserves and parks, is expected to lose its entire current range," WWF's report said.

Also at high risk were eight species of brightly coloured Hawaiian honeycreeper, Galapagos Islands penguins and the Scottish capercaillie -- the world's biggest grouse -- which WWF said could lose 99 per cent of its habitat because of warming.