Autumn bird migration typically peaks in the northern United States in late September and early October.
On Wednesday night, around 9:40 p.m. EDT, scientists estimated that 1.25 billion birds were in flight, mostly in the Southeast, where a northerly breeze behind a cold front helped birds move south for the winter.
BirdCast, a research consortium consisting of scientists from The Cornell Lab of Ornithology, Colorado State University and UMass Amherst, said on Facebook this was a new record, after the previous record of 1.23 billion was set on Sept. 25.
It was only the third night on record when the number of migrating birds surpassed one billion.
The BirdCast website uses weather radar and computer algorithms to estimate the number of birds and direction of flight during spring migration and produces a U.S. forecast for the night.
