Mysterious Night Wind

Seattle, Washington:
The new U.S. Weather Service radar on Camano Island and atmospheric profiler at Sand Point began to pick up a mysterious 20 mile per hour wind out of the south each night about a month ago, a wind that started about sunset and ended at dawn.

Forecasters finally realized the new instrument is almost too accurate for its own good: It was detecting no wind, but the annual nighttime migration of thousands of birds towards the north, said a meteorologist.