Every fall, the skies of the northeastern United States fill with warblers, barn swallows and other birds heading south to warmer climates. The journeys are long - often spanning continents - and birds often have to make many pitstops along the way. But climate change is disrupting these ancient migration routes, leaving birds without proper habitats, food and putting them at risk of extreme weather.
To better understand these disruptions, researchers at Binghamton University are actively studying how migratory birds are responding to environmental changes over time. This year, Associate Professor Emeritus of Biological Sciences Anne Clark and her colleagues launched a new research project to compile decades of data on red-winged blackbirds - some of it recorded as far back as the 1940s - which could highlight issues caused by climate change.
"It's a way to look at climate change. It's a way to look at how birds have responded to changing weather, but also how their reproductive success may have changed," said Clark. "So that's a long-term project to try to get a data on a very common bird where the research goes back, but it's never been pulled together to ask that question."
Following the flyways
Not every bird migrates for the fall, and for those that do, the distances vary. Some might make a short trek from New York to Pennsylvania, for example, whereas others might travel thousands of miles. Barn swallows, for instance, are "long-distance migrants" that journey all the way from New York to Argentina and Chile.
The birds that do migrate tend to fly specific flyways. Just as you would take a certain route to get to your destination, birds have their own "highways."
"There are actually well-organized, from our point of view, predictable spatial corridors going down across the nation," said Clark.
Just like a highway road trip, birds don't migrate from point A to point B without making a stop or two along the way. Birds will take a few "hops" south, and "tank up" at various stopover sites.
"These stopover sites act like a gas station. They stop over, fueling up on the energy that they need before they move again," said Justin Mann, a behavioral ecologist in the Department of Biological Sciences who studies how animals use environmental and social information when making fitness-related decisions.
But these long journeys are being disrupted by climate change. Birds, who base their travel plans on day length and other cues, might show up too late or too early to a habitat and/or find the bug they like to nibble on is no longer around or their preferred habitat isn't as it should be. Imagine, for example, taking a long road trip only to find all of the restaurants or hotels along the way are closed.
"They're often timing either using day length or temperature/weather where they are. That's supposed to predict the phenology - the basic reproduction of insects or plants - where they're going, and those can get asynchronized," said Clark. "Shorter-term migrants may be using conditions where they are to predict how good conditions are where they're going. And often, maybe counterintuitively, they want to arrive relatively early before the conditions get too hot and too dry, and if they're using the conditions where they are, they may be either too early or too late with respect to the weather when they get there."
"Birds are having to move to new areas because the current areas that they have inhabited for quite a long time are no longer suitable to their particular needs," added Mann.
A treacherous journey
Before birds can even arrive at their final destination, they might face even more difficult travel conditions along the way due to climate change.
Climate change has led to an increased frequency of extreme weather, noted Clark. As the hurricane season extends later and later, birds are more likely to encounter a storm just as they're trying to cross the Gulf of Mexico.
"Those migration periods might coincide with extreme weather events, which are becoming a lot more common," said Clark. "So even though that might not be something happening in New York, the birds that eventually make it to New York are having to deal with extreme weather events along their migration routes."
Protecting bird "gas stations"
Mann leads a class titled "Biology and Conservation of Birds," where he teaches the basic biology of birds and conservation issues. The class spends a good amount of time thinking about how climate change is impacting bird conservation.
A major thrust in conservation efforts, said Mann, is protecting habitats that are crucial to birds - those "gas stations" where birds fuel up along the way.
"There's lots of research on the areas that we need to conserve and protect that will give the most payoff, the most benefit, to birds who need those crucial stopover points," said Mann.
Clark said that if climate change is particularly devastating to an area in terms of habitat destruction, then being very careful about what kind of destruction humans actually do directly can make a big difference.
"Some birds have remarkably narrow, small places where they overwinter," said Clark. "So we can often identify specific habitats that are really worth concentrating on, to make good decisions about how not to allow that habitat to degrade."
Maintaining stopover sites for birds is also important. Mann points to one in Binghamton University's own backyard as a good example: the 190-acre Nature Preserve.
"One wonderful thing about the Nature Preserve is its proximity to the Susquehanna River," said Mann. "Many species use rivers as highways when they're migrating, so forests off of major rivers can be really, really important stopover sites. So the Nature Preserve is certainly an important forest for the birds who show up."
