Adaptive drift and barrier-avoidance by a fly-forage migrant along a climate-driven flyway

Abstract Background Route choice and travel performance of fly-forage migrants are partly driven by large-scale habitat availability, but it remains unclear to what extent wind support through regimes moulds their migratory behaviour. We aimed determine a trans-equatorial migrant engages in adaptive drift distinct biomes across Africa. The Inter-tropical Front (ITF) marks strong seasonally shifting climatic boundary at the thermal equator, we assessed whether detours were associated with this feature. Furthermore, sought disentangle influence biome on daily, regional seasonal performance. Methods GPS-tracked 19 adult Eleonora’s falcons Falco eleonorae from westernmost population Canary Islands 39 autumn 36 spring migrations Madagascar. Tracks annotated data assess falcons’ orientation behaviour they achieved each season biomes. further tested falcon routes Sahel correlated ITF position, how realized affect daily times, distances speeds. Results Changes Africa’s changes prevailing fields. Falcons higher along than was available shortest possible route drifting adverse fields, compromised while detouring supportive Movements Sahel-Sudan zone strongly position autumn, more individually variable spring. Realized an important driver speeds distances, conjunction wind-independent variation time budgets. Conclusions Although budgets vary independently wind, is affected orientation-dependent support. thereby tend minimize or avoid headwinds opposing fields over ecological barriers, compensating weak hospitable may offer leading line terms both flight foraging conditions.