Into turbulent air: Size-dependent effects of von Kármán vortex streets on hummingbird flight kinematics and energetics

Victor M. Ortega-Jimenez, Nir Sapir, Marta Wolf, Evan A. Variano, Robert Dudley

Research output: Contribution to journalArticlepeer-review


Animal fliers frequently move through a variety of perturbed flows during their daily aerial routines. However, the extent to which these perturbations influence flight control and energetic expenditure is essentially unknown. Here, we evaluate the kinematic and metabolic consequences of flight within variably sized vortex shedding flows using five Anna's hummingbirds feeding from an artificial flower in steady control flow and within vortex wakes produced behind vertical cylinders. Tests were conducted at three horizontal airspeeds (3, 6 and 9 m s-1) and using three different wake-generating cylinders (with diameters equal to 38, 77 and 173%of birds' wing length). Only minimal effects on wing and body kinematics were demonstrated for flight behind the smallest cylinder, whereas flight behind the medium-sized cylinder resulted in significant increases in the variances of wingbeat frequency, and variances of body orientation, especially at higher airspeeds. Metabolic rate was, however, unchanged relative to that of unperturbed flight. Hummingbirds flying within the vortex street behind the largest cylinder exhibited highest increases in variances of wingbeat frequency, and of body roll, pitch and yaw amplitudes at all measured airspeeds. Impressively, metabolic rate under this last condition increased by up to 25% compared with control flights. Cylinderwakes sufficiently large to interact with both wings can thus strongly affect stability in flight, eliciting compensatory kinematic changes with a consequent increase in flight metabolic costs. Our findings suggest that vortical flows frequently encountered by aerial taxa in diverse environments may impose substantial energetic costs.

Original languageEnglish
Article number20140180
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1783
StatePublished - 26 Mar 2014
Externally publishedYes


  • Calypte anna
  • Flight energetics
  • Stability
  • Turbulence
  • Vortex shedding
  • Wingbeat kinematics

ASJC Scopus subject areas

  • General Immunology and Microbiology
  • General Biochemistry, Genetics and Molecular Biology
  • General Environmental Science
  • General Agricultural and Biological Sciences


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