Field Flight Dynamics of Hummingbirds During Territory Encroachment and Defense

PLoS One. 2015 Jun 3;10(6):e0125659. doi: 10.1371/journal.pone.0125659. eCollection 2015.

Abstract

Hummingbirds are known to defend food resources such as nectar sources from encroachment by competitors (including conspecifics). These competitive intraspecific interactions provide an opportunity to quantify the biomechanics of hummingbird flight performance during ecologically relevant natural behavior. We recorded the three-dimensional flight trajectories of Ruby-throated Hummingbirds defending, being chased from and freely departing from a feeder. These trajectories allowed us to compare natural flight performance to earlier laboratory measurements of maximum flight speed, aerodynamic force generation and power estimates. During field observation, hummingbirds rarely approached the maximal flight speeds previously reported from wind tunnel tests and never did so during level flight. However, the accelerations and rates of change in kinetic and potential energy we recorded indicate that these hummingbirds likely operated near the maximum of their flight force and metabolic power capabilities during these competitive interactions. Furthermore, although birds departing from the feeder while chased did so faster than freely-departing birds, these speed gains were accomplished by modulating kinetic and potential energy gains (or losses) rather than increasing overall power output, essentially trading altitude for speed during their evasive maneuver. Finally, the trajectories of defending birds were directed toward the position of the encroaching bird rather than the feeder.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Behavior, Animal / physiology*
  • Birds / physiology*
  • Flight, Animal / physiology*

Grant support

This work was funded by Office of Naval Research (http://www.onr.navy.mil) MURI N000141010952 to TLH and 8 others and by National Science Foundation (http://www.nsf.gov/) IOS-1253276 to TLH. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.