Two ways in which global change may cause mismatch between cue and optimal migration timing (
). A) Conditions at the breeding grounds change from the blue to the red distribution so that T* is earlier than before. This implies that the optimal relationship prescribes earlier migration for a given cue (shift from blue to red relationship). Individuals that follow the old strategy (blue) arrive too late in the changed environment (red), and over time one would expect a change from the blue to the red strategy. B) The distribution of the cue changes in the area where the migration decision is made, but there is no change at the breeding grounds. Individuals with the old (blue) strategy now arrive too early. Again, a change from the blue to the red strategy over time would allow the migratory strategy to remain successful.