I don’t know if this is good news or bad news, but it’s certainly news. The ink is barely dry on a new scientific report about spring bird migration. Birds are returning to their nesting grounds earlier now, due to climate change. The good news: some species are adapting. The bad news: they are probably not adapting fast enough.
This latest study looked at 24 years of weather radar data, which is able to follow migration patterns across the entire continent. A team of scientists from Colorado State University, the Cornell Lab of Ornithology and the University of Massachusetts documented that birds are now passing migration checkpoints earlier than they did 20 years ago. Furthermore, the biggest changes appear to be happening in areas that are warming fastest.
It is no surprise that birds would adapt. Migration itself is probably the result of adaptation to prehistoric climate changes. Birds go wherever they can find food. Many of the birds we enjoy in Maine are happier to see our bug season than we are. But 20 years is a disturbingly short timespan for any species to adapt to abrupt climate change.
Phenology is the study of nature’s timing. Specific to Maine, when do our lakes thaw? When do our trees leaf out? When do the black flies torment? How did mayflies and June bugs get their names?
Phenology is critical to birds. For thousands of years, they’ve instinctively timed their migrations to arrive in North America when the banquet table was full. While flitting around the treetops in Panama, birds have no idea what conditions are like back home in their nesting areas. They don’t know that milder winters are leading to earlier plant blossoming and premature insect hatchings. They don’t know that the changing climate requires them to migrate earlier.
Instead, they find out the hard way. Birds arriving too early risk starvation. Conversely, birds arriving too late miss out on prime nesting sites and mating opportunities. Timing is everything. When the climate is warming, evolution favors the early-arrivers. When the climate is cooling, evolution favors the late-comers. Thus, species adapt slowly.
Bob Duchesne, Good Birding
Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. He developed the Maine Birding Trail, with information at mainebirdingtrail.com. He can be reached at email@example.com.
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