Fig. 1

Pathways of seasonal range colonisation in migratory species. Migratory innovation can occur when individuals or groups make novel movements (F1), which can arise from (a) exogenous mechanisms (e.g., drift by winds or geomagnetic anomalies), exploratory dispersal within a seasonal stage, or abmigration (following other species), as well as (b) through the emergence of novel endogenous navigation programmes. Successful colonisation depends on their offspring (F2) or other conspecifics repeating the novel migration route in subsequent years. In solitary migrants (c, d), innovations are unlikely to be transferred if they originate from stochastic drift or dispersal, as F2 individuals will continue to follow inherited programmes to the original range (c). Novel endogenous navigation programmes can similarly only be transferred to F2 in solitary migrants if they are genetically heritable (d). In social migrants (e, f), by contrast, route innovations can be transferred between generations if F2 individuals follow returning F1 innovators on return migrations, regardless of whether the initial innovation mechanism was stochastic e or endogenous f