Zebra finches have a problem: their eyes are too close together for good depth perception through stereovision. The distance up to which you can estimate depth from stereovision depends on the difference between the images from the two eyes. The closer together the eyes are, the more similar the images, the shorter the range in which stereovision works for you.
Luckily, you don’t need stereovision for depth perception. Instead of comparing the images between two eyes, you can compare the images between two time points while you’re moving! Taking this principle further, this means that the movement of the images on your retina (optic flow) already contains the necessary depth information. Depending on how the term is used, you could call this “motion parallax”. However, some researcher define it to demand the eyes to focus on an object. That’s not the case, here.
To see if zebra finches might be using this mechanism, we made them fly in a curve and measured the head movements. As is known from insects, the zebra finches held their heads (and thus their gaze) in a constant angle relative to the surrounding and only switched this angle when necessary (Eckmeier et al. 2008). This is probably due to the opto-collic reflex, which makes the bird’s head follow the turn of the surrounding and reset with quick (saccadic) turns in the opposite direction (Eckmeier and Bischof, 2008).
Finally, I recorded from a visual nucleus while playing the reconstructed birds-eye-view from those curved flights on a panoramic screen. The insights from this study were little, it was a purely exploratory study, but it included some very interesting recordings (Eckmeier et al., 2013).
The work was conducted at Bielefeld University, Germany. My adviser was Hans-Joachim Bischof and we worked in collaboration with Martin Egelhaaf and Roland Kern.