Watch these daredevil birds dive into chimneys en masse

During their fall migration south, thousands of chimney swift birds 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. Learn more: http://scim.ag/2l8eo9N