veery

The veery migrates from Delaware to South America every winter.

New research out of Delaware State University shows songbird behavior could help improve the accuracy of forecasting hurricane season.

LISTEN | DSU research links a bird's behavior to severity of hurricane season

Christopher Heckscher has been studying the "veery" bird for more than a decade when he noticed irregularities in its behavior and the timing of its breeding and nesting near White Clay Creek.

"Over time, the birds were doing different things in different years in terms of when they were nesting. I just started trying to figure out why they were showing different behaviors in some years than others," he said.

That's how he stumbled into the meteorological aspect. Every winter, the veery migrates from Delaware to South America, traveling a long migratory route that brings with it weather obstacles. They chart the treacherous course back to Delaware each spring just to lay one set of between two and four eggs annually.

"In some years, the female birds would nest longer than others; if they nest and their nest fails--say, it's attacked by a predator and they lose the young--they will re-nest, and supposedly, they should re-nest continually until they bring off a successful clutch, then they will go to molt their feathers and migrate," he said.

Heckscher has determined there's a direct correlation between the length of the breeding season and the severity of the Atlantic Hurricane season in years when the birds spent more time nesting.

"I don't know what they're sensing, but whatever it is, they know by the middle of May because that's the height, the peak of their breeding season," he said. "I don't know if it's something that they're keying in on in the winter in South America before they come up to North America, or whether it's something they sort of sense as they're migrating north, but clearly, something is affecting their physiology, and that's giving them the internal biological signal to stop nesting at a certain point."

He said, over time, birds that don't adjust their breeding cycle, which lasts between 30 and 40 days, likely have higher mortality rates during their fall migration as they head south during strong tropical storms.

"That's kind of weeded out the birds that weren't so good about sensing what's coming.

"More eggs might be a way that they compensate for higher mortality in the fall, if they can average more young in the spring before a bad hurricane season, than if they experience higher mortality during that bad hurricane season, that might kind of offset the mortality," he speculated.

He suspects other migratory birds, in addition to the veery, likely share this relationship.  

The veery population is declining, though, a pattern that been observed for long-distance migratory songbirds. In 1993, when he started this project, Heckscher said there were a lot more veery.

"I suspect that stronger hurricane seasons in recent years is probably having an effect," he said. "We haven't had a series of below-average hurricane seasons in quite awhile...the hurricane seasons are really difficult to predict; there doesn't seem to be any pattern."

Now, he'll take a closer look at weather patterns in South America and what's happening during their northward migration, climate-wise.

"One possibility is that the birds, when they head north across the Caribbean sea and Gulf of Mexico to get to North America, they may be sensing sea surface temperatures, and we already know that sea surface temperatures are correlated with hurricane activity, so it could be something as simple as that," he said. "Or it could be something really complex like precipitation affecting their food source in South America and that affecting their biochemistry somehow."

His research could have a major impact on meteorology.

"It is possible that these birds are using something in the environment that we have not discovered yet, and then, in turn, that could be helpful in meteorologists, increasing the accuracy of their models and predicting future hurricane seasons."

He stressed the need to listen to nature in these ways.

"It's really interesting to see how connected things are in the natural world, and we're a part of that natural world, and here we have a bird that can help us to understand how our natural world functions, and how we can sort of prepare for things like stronger hurricanes and more frequent hurricanes that obviously have implications for human health and survival as well," he told WDEL.