But for bird watchers, something confusing has been going on for years - bird species have increasingly been showing up where they don't seem to belong, reports CBS News correspondent John Blackstone.
Now scientists with the Audubon Society have taken four decades of bird-sighting records and like the house finch and the Steller's Jay have moved their winter homes hundreds of miles north.
In those same 40 years, the average January temperature in the United States has risen by almost five degrees.
As the temperatures have gone up the birds have gone north. Since the 1960s some species have changed their winter destination more than 400 miles.
Of 305 species studied more than half had moved north an average of 35 miles.
"It's a very strong indication that global warming is not something that's remote," said Reg Butcher of the National Audubon Society. "It's something that's been with us for the last 40 years."
In California, Audubon scientists went beyond bird movement to look for solutions. They found that reducing the greenhouse gas emissions that cause global warming can make a dramatic difference for many birds.
"California can really lead the way on this, but ultimately it's gonna have to be a global solution that we're looking at," said William Monahan of Audubon California.
While birds are moving to adapt to global warming Audubon scientists say climate change may be coming too quickly for some to survive.