Why Do Cranes Migrate in Small Groups and Leave at Separate Times?
"The fact that Whooping cranes have staggered departures helps the species survive. If they all flew together and encountered a blizzard, or
tornadoes, or if they arrived at the nesting grounds too early and couldn't find food in the ponds still covered with ice, the entire flock would be in peril. Even with different departure times, all the adult birds will need to reach the nesting grounds in time to nest because the northern summer is so short. For this reason, the Whooping cranes that depart from the Texas wintering grounds one or two weeks later than most will make a more rapid migration north and will nearly catch up with some of the birds that left first." —Biologist and Whooping Crane Coordinator Tom Stehn, USFWS