Data from: A novel system for bi-ocular eye-tracking in vertebrates with laterally placed eyes

1. Animals use vision to gather information about their environment and
then use that information to make behavioural decisions that affect
fitness. They will often move their heads or eyes to inspect areas of
interest with their centres of acute vision, such as foveae, to gather
high resolution information about potential mates, predation risks, or
other aspects of the environment. Few studies to date have been able to
accurately determine where laterally eyed animals direct their visual
attention and how they use their eyes to gather information. 2. We present
a non-invasive eye-tracking system that can simultaneously track the gaze
of two eyes. This is particularly useful for studying animals with
laterally placed eyes (most vertebrates) where the two eyes are viewing
different images. This system can also accommodate comparative studies
using animals of varying size, including small animals that are not
frequently used in eye-tracking studies due to constraints of existing
eye-tracking systems. We conducted an eye-tracking experiment with
European starlings (Sturnus vulgaris) to test the eye-tracking system,
calibration methods and highlight relevant aspects of experimental design.
3. We were able to accurately track the gaze of European starlings with
<5 degrees of error. We also found that starlings are more likely
to fixate on biologically relevant visual stimuli (e.g. predators and
active prey) than simple stimuli (e.g. a dot) in video playbacks. 4. The
method presented here can be used to address ecological and evolutionary
questions about where animals direct their attention and how they visually
inspect mates, food and predators, as well as address management questions
about how animals inspect man-made objects. This method can also be used
to answer fundamental questions about vision, such as how laterally eyed
vertebrates coordinate the use of their eyes laterally and binocularly.