Abstract
Fast moving animals depend on cues derived from the optic flow on their retina. Optic flow from translational locomotion includes information about the three-dimensional composition of the environment, while optic flow experienced during a rotational self motion does not. Thus, a saccadic gaze strategy that segregates rotations from translational movements during locomotion will facilitate extraction of spatial information from the visual input. We analysed whether birds use such a strategy by highspeed video recording zebra finches from two directions during an obstacle avoidance task. Each frame of the recording was examined to derive position and orientation of the beak in three-dimensional space. The data show that in all flights the head orientation was shifted in a saccadic fashion and was kept straight between saccades. Therefore, birds use a gaze strategy that actively stabilizes their gaze during translation to simplify optic flow based navigation. This is the first evidence of birds actively optimizing optic flow during flight.
Highlights
Navigating through a complex environment requires a specific set of information
Using accommodation mechanisms for distance estimation would be too slow for fast navigation in difficult and unknown terrain [1]
The experiments were performed with the zebra finch (Taeniopygia guttata), a small Australian songbird, raised and kept at the department’s animal care facilities
Summary
It is essential to quickly get an impression of the three dimensional composition of the environment This impression would consist of the distances between the observer and the objects in the environment, as well as among those objects. Using accommodation mechanisms for distance estimation would be too slow for fast navigation in difficult and unknown terrain [1]. Stereopsis works only within a limited spatial range depending on the distance between the eyes and the spatial resolution [3]. All these mechanisms are not ideal for distance estimation during fast navigation, especially in rapidly flying animals such as many birds
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