By Patricia Waldron Feb. 14, 2017
, 7:15 PM
During their fall migration
south, thousands of chimney swift birds (Chaetura
pelagica) gather in a tornadolike flock at dusk before dropping down a
chimney—five birds at a time—to roost for the night. But unlike European
starlings, which form massive daily flocks called murmurations, chimney swifts
are flocking amateurs that spend most of the year in small groups. To
understand how the birds manage this complex and rapid descent, researchers
focused three cameras on an 1800-strong flock of chimney swifts as they
funneled into an industrial chimney in downtown Raleigh, North Carolina. By
mapping the 3D position of each bird’s flight path, they found that swifts
adjust their route based primarily on their closest flying
neighbors, and ignore birds that are farther away, they report today in the
Proceedings of the Royal Society B. Whereas the outer circling is neat and
orderly, cooperation breaks down as birds near the chimney, and they make a
dash for the opening to get the best roosting sites. On occasion, these
rotating flocks will suddenly reverse direction midflight, or switch from
flying in circles to figure-eight patterns, causing the birds to dodge each
other. These “rules of the roost” could be used to program flocks of delivery
drones to ensure a well-organized return to the warehouse, while avoiding
expensive, midair collisions.
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