It pays to follow the leader: Metabolic cost of flight is lower for trailing birds in small groups

• 成果类型: Article
• 署名作者: Friman, Sonja I.; Elowe, Cory R.; Hao, Siyang; Mendez, Laura; Ayala, Raul; Brown, Ian; Hagood, Caylan; Hedlund, Yseult; Jackson, Dayna; Killi, Justin; Orfanides, Gabriella; Ozcan, Evrim; Ramirez, Jared; Gerson, Alexander R.; Breuer, Kenneth S.; Hedrick, Tyson L.; Edwards, V.
• 署名单位: University of North Carolina; University of North Carolina Chapel Hill; University of Massachusetts System; University of Massachusetts Amherst; Brown University; Howard University; Rochester Institute of Technology; University of Southern California
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-8610
• DOI: 10.1073/pnas.2319971121
• 发表日期: 2024-06-25
• 关键词: energy savings; wind-tunnel; pigeons; speed; range

摘要

Many bird species commonly aggregate in flocks for reasons ranging from predator defense to navigation. Available evidence suggests that certain types of flocks-the V and echelon formations of large birds-may provide a benefit that reduces the aerodynamic cost of flight, whereas cluster flocks typical of smaller birds may increase flight costs. However, metabolic flight costs have not been directly measured in any of these group flight contexts [Zhang and Lauder, J. Exp. Biol. 226 , jeb245617 (2023)]. Here, we measured the energetic benefits of flight in small groups of two or three birds and the requirements for realizing those benefits, using metabolic energy expenditure and flight position measurements from European Starlings flying in a wind tunnel. The starlings continuously varied their relative position during flights but adopted a V formation motif on average, with a modal spanwise and streamwise spacing of [0.81, 0.91] wingspans. As measured via CO 2 production, flight costs for follower birds were significantly reduced compared to their individual solo flight benchmarks. However, followers with more positional variability with respect to leaders did less well, even increasing their costs above solo flight. Thus, we directly demonstrate energetic costs and benefits for group flight followers in an experimental context amenable to further investigation of the underlying aerodynamics, wake interactions, and bird characteristics that produce these metabolic effects.