In the 19th century observers reported birds at oil-burning lighthouses and lightships. Rom the moment humans first set artificial light against darkness, we have sensed that birds move at night. Habitat destruction, collisions with buildings, declines in insect abundance-the threats to migrants are many, and the question has become: Can new tracking technologies help to unravel the mysteries of nocturnal migration while we still have time to preserve one of the world’s great natural wonders? Some three billion birds have disappeared from North America in the past 50 years, and migrant species in particular have suffered significant losses. This age has dawned at a critical time for conservation. “It really is a new golden age of observation,” says Cornell University ornithologist Andrew Farnsworth. Community science is helping fill in the picture on the ground, identifying previously unknown perils and places critical to migrants’ survival. Advances in the use of weather surveillance radar now offer images of millions of birds on the move, while new tracking technologies trace the long aerial paths taken by individuals. In the past few years, scientists have gained an unprecedented window into the phenomenon of nocturnal migration. “And we’re making new discoveries all the time.” “The more you can see what’s going on, the more fascinating it becomes,” says Jeffrey Buler, a University of Delaware wildlife ecologist. Even for those who study migration, the story is unfolding in ways never before possible. Meanwhile we humans by and large have no inkling of the tremendous journeys made while we sleep. The reasons include a calmer atmosphere, guidance from the stars, and safety from predators. While some large birds like hawks, cranes, and waterfowl are daytime travelers, most migrants-including the vast majority of songbirds-are on the wing in the dark. Pull back: The continent becomes a beating heart, the birds its blood pulsing back and forth, a mystery we’re just beginning to understand.īillions of birds travel north in spring and south in fall, hundreds of species keeping a cycle of movement, and they do so primarily at night. Zoom in: That single bird spreads its wings, joining thousands upon thousands of birds spread across the night sky. The birds will flow through the sky, a living river rolling through darkness, skirting storms and artificial light and a minefield of inhospitable landscapes below. Or a Bobolink, a Scarlet Tanager, a Wilson’s Warbler .Tonight, conditions seem right. Or a Yellow-billed Cuckoo leaving the Bolivian plains, bound for the deciduous woodlands of Illinois, some 4,000 miles away. Or a Blackpoll Warbler in an orange grove in Colombia, set to make a 6,000-mile journey to Canada’s boreal forest. Maybe an Upland Sandpiper standing on the vast Argentine pampas, ready to launch itself on an 8,000-mile trek to its breeding grounds on Alaska’s upland tundra. Imagine a single bird during a spring dusk moments before flight.
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