Stopover territoriality in songbirds crossing the Sahara: aggression and energetics during migration

Abstract Stopover territoriality, i.e., the defense and broadcast of an ephemeral home range during avian migration, is rare or perhaps overlooked. However, settling on a territory may allow for easier access to resources therefore promote faster refueling despite added costs defense. We examined occurrence stopover territoriality its relationship body condition rates. color-ringed Western Subalpine Warblers ( Curruca iberiae ) mapped their ranges measured associated habitat characteristics spring in Sahara. simulated intrusions via song playback quantify territorial behavior. Males aggressively defended broadcasted territories response intruders. Initial males was negatively related vegetation density, suggesting that higher are selective certain features. Low density does not support selection foraging, but social monitoring predator vigilance as functions. Fuel deposition rates recaptured were unrelated characteristics. Female did use repeated yet had similar rates, conditions, durations males. Therefore, while selected based condition, influence expressed reduced migratory characteristics, making prolonged stopovers up 27 days with low maintaining defending territories. These results suggest some individuals staging non-energetic reasons, such pre-breeding preparations, transitioning between breeding life history stage. Significance statement Territoriality birds commonly activities, less so wintering period rarely periods. migration be energetically beneficial. During trans-Saharan stopover, male warblers establish defend temporary by singing engaging physical ranges, those better occupied sparser vegetation. Females refueled at increase food-rich patches, aided efficient preparations approaching season. This first detailed documentation potential functions, benefits inform studies full-annual cycles histories many species.