Empirical Evidence for Energy Efficiency Using Intermittent Gliding Flight in Northern Bald Ibises

Birds face exceptionally high energy demands during their flight. One visible feature of some species is alternating between flapping and gliding, which should allow them to save energy. To date, there no empirical evidence an energetic benefit this. understand the physiology behind strategy, we equipped hand-raised Northern Bald Ibises ( Geronticus eremita ) with data loggers human-guided migration. We monitored position birds, wingbeats, overall dynamic body acceleration (ODBA), heart rates as a proxy for expenditure. The expenditure was significantly affected by length gliding bouts. A pronounced decrease in rate measured after already 1 s gliding. Additionally, at bouts up 30 increased steadily but stabilized thereafter. gilding proportion intermittent flight saving compared continuous flapping. At about 20%, maximum 11% based on measurement. higher proportions, additional negligible. Furthermore, flight, not all used mechanical work, found greater ODBA different proportions rate. Nevertheless, combination two methods essential determine birds’ movement This study provides that energetically beneficial can reduce costs flights.