When people hear the term “fallout,” they usually think of windborne nuclear particles. But for avid birders, an avian fallout is more electrifying than radioactive rainfall. Kids may have visions of gifts stacked beneath the Christmas tree. And skiers may whoop with joy over a fresh blanket of snow. But birders dream of phenomenal spring fallouts when every shrub and tree seems to drip with birds.
For migrating birds, fallouts are among the hardships that make migration so perilous. Fallouts are usually caused by cold fronts and weather patterns that disrupt their arduous flights to and from summer breeding grounds.
Most songbirds migrate at night when they are less vulnerable to daytime predators. Cooler nighttime temperatures also allow them to travel farther and longer without overheating. But sometimes nature intervenes with strong, buffeting winds that blow birds off course. Severe head winds can quickly drain a bird’s energy reserves, and they look for protective cover. But slow descents make them vulnerable to opportunistic predators, including gulls, all too ready to take advantage of their weakened condition. Instead, they maintain speed and altitude until they are directly above protective cover. Then, they simply fold their wings and drop like stones. Birders call this a “fallout,” because birds seem to rain from the sky.
My wife Sandy and I have witnessed spectacular spring fallouts in New England, Texas and the Dry Tortugas off the coast of Florida.
The eastern seaboard from Washington, D.C., to Boston is almost a continuous city. Some refer to it as “Boswash.” Canopied islands of green like Mount Auburn Cemetery in Cambridge, Mass., are a magnet for migrating birds and a popular destination for birders chasing spring warblers. During a major fallout, it’s a magical place. Sandy and I have witnessed fallouts there with counts as high as 20 species of warblers.
We have also watched spring warbler migrations from places like Mohegan Island, off the coast of Maine. Warblers near exhaustion after long flights over open water often take refuge in the lobster traps stacked near the dock. Birds also hitch rides on passing boats. They may hide between your feet for protection from the gulls.
High Island near the Texas coast is famous for fallouts as migrating birds drop into their cover after a long, exhausting flight across the Gulf of Mexico. We’ve seen fallouts there when warblers were underfoot almost everywhere. We’ve seen similar fallouts at Point Pelee National Park in Canada, where migrating birds recover from long flights across Lake Huron.
One spring, Sandy and I joined a WINGS-guided tour to the Dry Tortugas, a cluster of small islands off the Florida Keys. High winds made the seas so rough that nights aboard our boat were mostly sleepless. But winds were a mixed blessing for birders. Because of the weather, large numbers of birds were trapped on the islands and starving. It was an extraordinary but heartbreaking opportunity to observe myriad species of warblers, swallows and other songbirds too weak to fly or hide. Falcons ate their fill, and cattle egrets and gulls devoured defenseless birds as they sauntered casually through the grounds of Fort Jefferson. Our only consolation was that the birds were victims of nature, not the foolishness of humans.
