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Follow the Leader
How birds migrate between wintering and breeding grounds, often over thousands of kilometers through difficult conditions, remains mysterious. The recovery of North American Whooping Cranes by release of captive-reared birds trained to migrate by following aircraft provided an opportunity for Mueller et al. (p. 999; see the cover) to analyze 8 years of data for individual birds. The presence of older birds within a group of migrating cranes significantly decreased the deviations the flock took from a straight line migration path. The lack of evidence for a genetic component indicates that social learning dominates any innate capacity in developing migratory behavior.
Successful bird migration can depend on individual learning, social learning, and innate navigation programs. Using 8 years of data on migrating whooping cranes, we were able to partition genetic and socially learned aspects of migration. Specifically, we analyzed data from a reintroduced population wherein all birds were captive bred and artificially trained by ultralight aircraft on their first lifetime migration. For subsequent migrations, in which birds fly individually or in groups but without ultralight escort, we found evidence of long-term social learning, but no effect of genetic relatedness on migratory performance. Social learning from older birds reduced deviations from a straight-line path, with 7 years of experience yielding a 38% improvement in migratory accuracy.