Every spring and fall, Golden-winged Warblers undertake a perilous, nonstop journey across the Gulf of Mexico. For a bird that weighs about as much as two nickels, this 800+ mile overwater crossing is a high-stakes gamble that leaves no room for error. A new scientific study by Audubon and many partners sheds fresh light on how these warblers decide when to make that leap, and what a changing climate could mean for their future. 

Researchers analyzed geolocator data from 89 Golden-winged Warblers, some of which we helped tag in North Carolina starting in 2013. We wanted to understand how weather conditions around the Gulf of Mexico influenced the crossing of these tiny warblers during migration. 

A perilous journey 

They begin moving south in September, flying straight across the Gulf of Mexico to Central and South America. The geolocator backpacks we specially designed for them have gathered data from these cross-continent, thousand-mile-long journeys so we know the exact route these birds take.  

The light-level geolocators on the birds' backs estimate their location by using a light sensor and internal clock to identify sunrise and sunset. That data is then used to calculate latitude and longitude and develop a migration pathway for each individual bird. 

Researchers found that the movement of Golden-winged Warblers across the Gulf of Mexico is different from spring to fall and could be negatively impacted by severe weather conditions. This is especially true in the spring, when birds are returning to their breeding sites. 

“We found that in the spring, Golden-wings aren’t as concerned with weather conditions, often wanting to arrive at their breeding destinations as quickly as possible,” Smalling said. “But a changing climate that brings increased humidity and more severe storms may decrease favorable conditions and negatively affect populations.”  

It all has to do with how birds stay cool: by breathing and panting to move air through their system. But humidity makes it hard for birds to do this. When humidity is high, they may fly higher to try to avoid it, or slow down to prevent overheating.  

A decrease in favorable conditions like this could delay crossings and increase mortality risk if birds can’t make the crossing safely.  

This finding isn’t surprising but does raise alarm bells for this already declining species. That’s why we're working to increase survey efforts in the state, build relationships with landowners through our new partnership with EcoForesters, and work with foresters to increase suitable habitat. 

A tiny, charismatic bird 

Golden-winged Warblers spend the breeding season in the leafy, young forests of Appalachia and the Great Lakes region, including western North Carolina, where they establish nesting territories and raise young. They return to the same sites' year-after-year, which is why habitat management is so important. If a nesting territory becomes too overgrown, Golden-wings disappear. 

“Golden-wings are an extremely beautiful and charismatic bird with very specific habitat needs,” said Curtis Smalling, Audubon North Carolina Executive Director and co-author on the paper. “Without careful monitoring and management, we could lose them in North Carolina altogether.”  

That’s why we’ve developed and coordinated a yearly survey for the bird, as well as partnerships with landowners so we can help manage and protect important habitat for these warblers.