Visual Guidance and Collision Avoidance in Birds:

In Collaboration with scientists at the Queensland Brain institute at the University of Queensland and the Queensland University of Technology I am investigating the ability of birds to avoid mid air collisions, when facing incoming obstacles or other birds, as well as general principles of visual guidance. The aim of this study is to gain a better understanding of how birds manage to avoid such collisions and derive simple rules for collision avoidance that would enhance the safety of commercial air travel and inform the development of guidance systems for unmaned aerial vehicles.

Flight at distinct speeds:

The flight of buderigars was filmed as they flew through a tapered tunnel. Unlike flying insects - which vary their speed progressively and continuously by holding constant the optic flow induced by the walls - the birds showed a tendency to fly at only two distinct, fixed speeds. They switched between a high speed in the wider section of the tunnel, and a low speed in the narrower section. The transition between the two speeds was abrupt, and anticipatory. The high speed was close to the energy-efficient, outdoor cruising speed for these birds, while the low speed was approximately half this value. This is the first observation of the existence of two distinct, preferred flight speeds in birds. A dual-speed flight strategy may be beneficial for birds that fly in varying environments, with the high speed set at an energy efficient value for flight through open spaces, and the low speed suited to safe manoeuvring in a cluttered environment. The constancy of flight speed within each regime enables the distances of obstacles and landmarks to be directly calibrated in terms of optic flow, thus facilitating simple and efficient guidance of flight through changing environments. More information is available here

Visual Control Of Flight Speed:

We have investigated whether, and, if so, how birds use vision to regulate the speed of their flight. Budgerigars, Melopsittacus undulatus, were filmed in 3-D using high-speed video cameras as they flew along a 25 m tunnel in which stationary or moving vertically oriented black and white stripes were projected on the side walls. We found that the birds increased their flight speed when the stripes were moved in the birds' flight direction, but decreased it only marginally when the stripes were moved in the opposite direction. The results provide the first direct evidence that Budgerigars use cues based on optic flow, to regulate their flight speed. However, unlike the situation in flying insects, it appears that the control of flight speed in Budgerigars is direction-specific. It does not rely solely on cues derived from optic flow, but may also be determined by energy constraints. More information is available here

Inflight Body Awareness in Budgerigars:

Budgerigars interrupt their normal wing-beat cycle when encountering passages that are narrower than their wingspan. The birds raise their wings or tuck them against their body, to prevent contact with the flanking panels. Our results suggest that the birds are capable of estimating the width of the gap with high precision: a mere 6% reduction in gap width causes a complete transition from normal flight to interrupted flight, vastly exceeding the performance of humans in similar experiments. More information is available here

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