"This is as close as science at this scale gets to proof," said Greg Butcher, the lead scientist on the study and the director of bird conservation at the Audubon Society. "It is not what each of these individual birds did. It is the wide diversity of birds that suggests it has something to do with temperature, rather than ecology."
Of course, observant birders have been saying this for years—a friend of mine who's lived in Duluth on and off for about twelve years says that when she first moved up here, cardinals showed up this far north only rarely, and now they are a regular occurrence. But it's great to have a detailed, scientific study to back us up—here's hoping it translates into some real change. Audubon put together a nice website on birds and climate change with the full report, plus maps and species highlights, and it is definitely worth checking out.
The data for this study was collected from Christmas Bird Counts, a citizen science program that is over a hundred years old and is exactly what it sounds like—people go out around Christmastime and count birds. I participated one year, but normally the local count is on a Saturday and I have to work. But it's a lot of fun, nosing around the forest to see what you can see, and then later going to the compilation or reading the report to see what everybody else saw. Trained scientists can't possibly be everywhere to gather this data, and so volunteer efforts like the CBC are invaluable.
Wanna participate but don't want to wait around ten months for the next CBC? The Great Backyard Bird Count is this weekend, February 13th through the 16th. You can define "backyard" however you want (actual yard, local park, nature reserve, office window, etc.) and can count for as little as 15 minutes or as long as you want. Send in your results, and Audubon and the Cornell Lab of Ornithology will compile the data to see how birds are surviving the winter and where they are spending it.