Optimal Trajectories for the Short-Distance Foraging Flights of Swans

✍ Scribed by JAMES A POWELL; KATHARINA A.M ENGELHARDT

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 280 KB
• Volume: 204
• Category: Article
• ISSN: 0022-5193
• DOI: 10.1006/jtbi.2000.2026

✦ Synopsis

Optimal #ight theory relates body measurements (wing span, body cross-section, body mass) and aerodynamic variables (air density, drag, pro"le and induced power ratios) to the most energy-e$cient velocity for long distance migration. For short-range (2}10 km) foraging #ights the theory is expanded to include non-negligible costs for take-o! and energy savings/losses for climbing to altitude (drag decreases with air density and therefore with altitude). The theory predicts clear di!erences between Tundra and Trumpeter swans. Generally speaking, for #ights between 2 and 10 km Trumpeter swans can be expected to #y approximately 5}10 m lower in altitude and 1}2 m s\ more slowly than Tundra swans. Moreover, the total energy required for these foraging #ights is approximately 150% larger for a Trumpeter than a Tundra swan (80 vs. 120 kJ of direct mechanical energy for a 5 km #ight), suggesting that Trumpeter swans may be less inclined to take-o! than Tundra swans. These factors indicate that even Trumpeters native to the area (as opposed to recently translocated) would be more vulnerable to hunting than native Tundra swans. The expanded theory is compared to observations made in Utah's Bear River Migratory Bird Refuge.