(BALTIMORE SUN) — What’s that saying about leading a horse to water? The latest effort to teach Maryland-bred whooping crane chicks to migrate to Florida for the winter has been called off because the endangered birds will no longer follow the ultralight aircraft leading them.

Operation Migration, the nonprofit group that’s been guiding captive-bred young cranes for a decade on their initial 1,300-mile flight from nesting grounds in Wisconsin, has called it quits this year in Alabama, 500 miles short of the destination. While previous flights haven’t gone smoothly, either, this is the first time the group hasn’t succeeded in ultimately completing the journey to join the rest of the whooping crane flock wintering on the Gulf coast of Florida.