Background: It has been possible to teach a migration route to a flock of birds, for example in re-introduction schemes. After a trial with Canada geese Branta canadensis, microlight aircraft were used in the US to teach safe migration routes to reintroduced whooping cranes Grus americana.
Question: What did they use to teach birds a migration route?
Answer:<extra_id_0>.
<extra_id_0> microlight aircraft<extra_id_1>