Abstract
We present a Stackelberg game model to investigate how individuals make their decisions on timing and route selection. Group formation can naturally result from these decisions, but only when individuals arrive at the same time and choose the same route. Although motivated by bird migration, our model applies to scenarios such as traffic planning, disaster evacuation, and other animal movements. Early arrivals secure better territories, while traveling together enhances navigation accuracy, foraging efficiency, and energy efficiency. Longer or more difficult migration routes reduce predation risks but increase travel costs, such as higher elevations and scarce food resources. Our analysis reveals a richer set of subgame perfect equilibria (SPEs) and heightened competition, compared to earlier models focused only on timing. By incorporating individual differences in travel costs, our model introduces a "neutrality" state in addition to "cooperation" and "competition."