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How our unseasonably warm fall is affecting migratory birds

Oct 18, 2016

2016 has been on a record-breaking warm streak, according to the National Oceanic and Atmospheric Administration. 

So what does this unseasonably warm fall mean for birds that need to start packing up and heading south?

Andrew Farnsworth is a research associate with the Cornell Lab of Ornithology, and he runs BirdCast – it’s a tool the lab created to forecast what’s happening with bird migration each week. 

He says how weather patterns affect birds varies by species. 

“Some birds are dramatically affected, in that, for example, in the fall, species may stay around quite a lot longer than they might otherwise if temperatures are warmer. For example, waterfowl: common loon, ducks on the Great Lakes, if temperatures are warmer than average all the way through the fall and into early winter, those birds will stick around much, much longer than they would if there were a freeze,” he says.

Some species are less affected by temperature, and instead time their trips south based on changes in the amount of daylight, such as warblers that breed in the forests of the northern Midwest and Canada.

“Many of these birds are what we call calendar migrants, so they depart and arrive, and time their movements on a larger scale basically by the amount of daylight there is,” he says.

Farnsworth says our changing climate is already causing some species, such as Canada geese and turkey vultures, to transition from being migrants to residents.

He says other species can get knocked off-kilter.

“For birds that are doing these calendar movements, they can get horribly asynchronous with the resources around them," says Farnsworth. "So they can depart much earlier than they might need to, they can arrive much earlier than they should in the spring, and if the prevailing temperatures are either different or more severe storms exist, there can be big problems.”

Farnsworth says that while in general, birds are able to respond quickly to changes, they might not be able to keep up with the pace of human-caused climate change.

“It’s really a wild card that depends on the species itself in terms of how climate change is going to play out,” he says.