Swifts' migratory behavior may have conservation implications

Resembling swallows but more closely related to hummingbirds, swifts have unique migratory behavior, roosting for days at a time in chimneys or hollow trees along their migratory route in groups of hundreds or thousands of individuals. Little is known about whether groups that travel and roost together during migration are all from the same wintering site or are made up of individuals from across their winter range. A 2012 mortality event in British Columbia that killed more than 1,300 migrating