The barn swallow's migration between Europe and southern Africa involves extraordinary challenges. Understanding individual bird welfare during migration informs conservation of the full flyway.
Swallow welfare during Sahara crossing represents extreme physiological challenge at the individual level. Birds that begin the crossing with insufficient fat reserves experience progressive energy deficit, reducing flight capacity and ultimately causing death. Individual birds that survive do so by drawing down protein from muscle and organ tissue as fat reserves are depleted. Conditions on staging grounds in the Sahel - drought, food availability - directly determine individual crossing survival. Conservation of Sahel staging habitat is as important for swallow welfare as maintaining breeding habitat in Europe.