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Many species of birds stabilize their head while hovering,walking and while perched on moving strata such as branches.We study the way they perform this feat,and examine the reasons for this stabilization in terms of the aerodynamics involved,and the control system requirements.This study is based on laboratory and field experiments(see example picture below).While among perched birds there are no specific weight limitations,and walking birds have to perform saccadic motions to compensate for the horizontal motion,kingfishers are of special interest as they perform head stabilization over bodies of water at heights of up to 10 m,in order to identify fish,as the sensing requirements for stabilizing over water are much more complex.This means that map-fixing and map reading is not an option as the ripples and waves on the water surface cause the mapped surface to change almost randomly,resulting in the need for an independent,internally based position fixing mechanism.Quantitative field observations show that the kingfishers adjust to both the position of the sun and to the direction of the wind,by flapping into the wind,while tilting their head to minimize glare.This adds complication to the aerodynamics,causing asymmetric effects on the wings which add to the internal computation needs of the bird.Some preliminary results show a preferential head tilt,which allows better vision at the high angles of attack required for lift production in hovering(similar to the Concorde tilting the cockpit downwards during takeoff and landing).This tilt also helps reduce the asymmetric effect of the wind,by having the wake from the head move under the wings over much of the beat cycle.Combining these results with previous work on Kestrels and various land-based perching birds point to possible applications for hovering UAVs in natural situations.