Flight mechanics and control of escape manoeuvres in hummingbirds. II. Aerodynamic force production, flight control and performance limitations.
The superior manoeuvrability of hummingbirds emerges from complex interactions of specialized neural and physiological processes with the unique flight dynamics of flapping wings. Escape manoeuvring is an ecologically relevant, natural behaviour of hummingbirds, from which we can gain understanding into the functional limits of vertebrate locomotor capacity. Here, we extend our kinematic analysis of escape manoeuvres from a companion paper to assess two potential limiting factors of the manoeuvring performance of hummingbirds: (1) muscle mechanical power output and (2) delays in the neural sensing and control system. We focused on the magnificent hummingbird (Eugenes fulgens, 7.8 g) and the black-chinned hummingbird (Archilochus alexandri, 3.1 g), which represent large and small species, respectively. We first estimated the aerodynamic forces, moments and the mechanical power of escape manoeuvres using measured wing kinematics. Comparing active-manoeuvring and passive-damping aerodynamic moments, we found that pitch dynamics were lightly damped and dominated by the effect of inertia, while roll dynamics were highly damped. To achieve observed closed-loop performance, pitch manoeuvres required faster sensorimotor transduction, as hummingbirds can only tolerate half the delay allowed in roll manoeuvres. Accordingly, our results suggested that pitch control may require a more sophisticated control strategy, such as those based on prediction. For the magnificent hummingbird, we estimated that escape manoeuvres required muscle mass-specific power 4.5 times that during hovering. Therefore, in addition to the limitation imposed by sensorimotor delays, muscle power could also limit the performance of escape manoeuvres.
Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802, USA buc10@psu.edu.
Bo
0000-0002-6982-0811
B
Cheng
Field Research Station at Fort Missoula, Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA.
Bret W
BW
Tobalske
Biology & Chemistry Department, George Fox University, Newberg, OR 97132, USA.
Donald R
DR
Powers
Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA.
Tyson L
TL
Hedrick
School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA.
Yi
Y
Wang
Hummingbird Monitoring Network, PO Box 115, Patagonia, AZ 85624, USA.
Susan M
SM
Wethington
School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA.
George T-C
GT
Chiu
School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA.
Xinyan
X
Deng
D000054:Acceleration; D000818:Animals; D001696:Biomechanical Phenomena; D001717:Birds / Q000502:physiology*; D004924:Escape Reaction / Q000502:physiology*; D005426:Flight, Animal / Q000502:physiology*; D008954:Models, Biological; D009132:Muscles / Q000033:anatomy & histology / Q000502:physiology; D009929:Organ Size; D012399:Rotation; D013997:Time Factors; D035501:Uncertainty
Aerodynamics; Dynamics; Muscle; Neural delay; Power; Scaling