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Empirical Evidence for Energy Efficiency Using Intermittent Gliding Flight in Northern Bald Ibises
Ortal Mizrahy-Rewald Waldrappteam Conservation & Research
University of Veterinary Medicine Vienna
Bernhard Voelkl University of Bern
University of Veterinary Medicine Vienna / University of Vienna,
Alexei L. Vyssotski ETH Zurich
University of Veterinary Medicine Vienna / Waldrappteam Conservation & Research
Johannes Fritz Waldrappteam Conservation & Research
Frontiers Media Sa
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 is no empirical evidence of an energetic benefit to this. To understand the physiology behind the strategy, we equipped hand-raised Northern Bald Ibises (Geronticus eremita) with data loggers during human-guided migration. We monitored the position of the birds, wingbeats, overall dynamic body acceleration (ODBA), and heart rates as a proxy for energy expenditure. The energy expenditure was significantly affected by the length of flapping and gliding bouts. A pronounced decrease in heart rate was measured after already 1 s of gliding. Additionally, the heart rate at flapping bouts up to 30 s increased steadily but stabilized thereafter. The gilding proportion during intermittent flight affected the energy saving compared to continuous flapping. At a gliding proportion of about 20%, we measured a maximum of 11% saving based on heart rate measurement. At higher gliding proportions, the additional energy saving was negligible. Furthermore, as during flight, not all energy is used for mechanical work, we found a greater decrease rate of ODBA at different gliding proportions compared to heart rate. Nevertheless, the combination of the two methods is essential to determine birds' movement and energy expenditure. This study provides empirical evidence that intermittent flight is energetically beneficial and can reduce the high costs of flights.
Englisch
2022
Dieses Werk bzw. dieser Inhalt steht unter einer
CC BY 4.0 - Creative Commons Namensnennung 4.0 International Lizenz.
CC BY 4.0 International
http://creativecommons.org/licenses/by/4.0/
Geese Branta-Leucopsis; Doubly Labeled Water; Heart-Rate; Oxygen-Consumption; Metabolic-Rate; Expenditure; Behavior; Birds; Accelerometry; Acceleration