Visual versus visual-inertial guidance in hawks pursuing terrestrial targets

Area of Science:

• Comparative biology
• Avian predatory behavior
• Biophysics of flight

Background:

• Falcons use proportional navigation (PN) for aerial interception, relying on visual-inertial sensing.
• Hawks employ a mixed guidance (MG) law for terrestrial pursuits, integrating line-of-sight rate and velocity-deviation angles.
• The sensory basis for hawk pursuit guidance remains unclear, specifically whether visual information alone suffices.

Purpose of the Study:

• To investigate if Harris' hawks can control aerial pursuit using only visual information.
• To compare the efficacy of proportional navigation and mixed guidance models in explaining hawk flight trajectories.
• To determine if visual cues from target motion relative to background can substitute for visual-inertial data in hawk guidance.

Main Methods:

• High-speed motion capture of 228 flights from 4 Harris' hawks (Parabuteo unicinctus).
• Analysis of flight trajectories using proportional navigation and mixed guidance models.
• Comparison of model fits when visual-inertial data is replaced by visual-only target motion cues.

Main Results:

• Both proportional navigation and mixed guidance models adequately describe Harris' hawk trajectories.
• The mixed guidance model accurately predicts flight paths even when visual-inertial line-of-sight rate is substituted with visual target-background motion.
• While visual-inertial mixed guidance offers the best fit, all tested models provide a reasonable phenomenological explanation.

Conclusions:

• Harris' hawks' aerial pursuit may be controlled using visual information alone, particularly through target-background motion cues.
• Mixed guidance appears to be a flexible control strategy for hawks, adaptable to different sensory inputs.
• Further research is needed to elucidate the specific physiological pathways underlying these distinct guidance strategies.