Grey jay birds that store frozen food to help survive icy winters are dying out in parts of North America because global warming is rotting their hoards, a scientist said.
OSLO Grey jay birds that store frozen food to help survive icy winters are dying out in parts of North America because global warming is rotting their hoards, a scientist said.
The jay's dependence on natural refrigeration -- of food ranging from berries to insects -- make it an odd exception to a general rule that animals and plants survive better during less harsh winters.
"The hoards are turning into a bad investment because the food is rotting," said Thomas Waite, a researcher from Ohio State University of a 25-year study of the birds.
"The birds are getting less food and they may also suffer from food poisoning from eating rotten food," he told Reuters. Grey jays are about 30 cms (1 foot) long, roughly the size of a blackbird or American robin.
He said it was a rare case of climate change at one part of the year affecting success in breeding months later. "Warm autumns are hostile to the jays because they rely on a cold climate and cold storage," he said.
"The freeze-up of local lakes used to be in November, now it's happening more frequently in December," he said of research just published with colleague Dan Strickland in the journal Proceedings of the Royal Society B.
The birds were in danger of dying out on the southern edge of their range, mostly southern Canada but also parts of the United States including Maine, Vermont and Rocky Mountain states, because of the warmer autumns, he said.
Many scientists say a build-up of greenhouse gases released by burning fossil fuels in power plants, factories and cars is driving up world temperatures. In turn, that could trigger more floods, heatwaves and droughts and raise sea levels.
Grey jays can stash away tens of thousands of food items -- blueberries, beetles, even strips of meat from a carcass of a moose killed by wolves -- in pine trees around their territories to help them get through the winters.
They nest earlier than most other birds and rely on stores of frozen food to feed young, which typically hatch in April. "Jays can sit on eggs or even have nestlings with snow about," Waite said.
The scientists found that birds had more young in years after a cold autumn than a warm autumn. And birds living near an extra source of winter food -- like a bird feeder by a house -- did better after a warm autumn than those in a remote forest.
And similar woes might also affect other hoarders, such as squirrels, Waite said. Squirrels, however, may be less vulnerable because they rely on nuts that do not rot as easily as berries or meat.