快猫短视频

It鈥檚 difficult to focus your gaze on an object when your eyes are on opposite sides of your head. When European starlings want to focus their gaze, they do so in a unique way: rapidly bobbing their heads from side to side so both eyes get a look.

We humans have our eyes on the front of our heads, so their fields of vision overlap, but most birds have theirs on the sides. 快猫短视频s have proposed three ways they might focus on an object: use just one eye, look at the object through the small area above their beak where they do have binocular vision, or alternate between using the left and right eye.

All three methods would ensure that the most sensitive area of the retina, the fovea, is doing the looking.

But when of Purdue University in West Lafayette, Indiana and her colleagues tracked the gazes of European starlings () using video cameras, they found the birds did not use of any of these strategies.

Instead, they used a previously unknown strategy that the team calls 鈥渕onocular alternating fixation鈥�. The starlings look several times with one eye, then turn their head so the other eye can take several looks, and so on. This results in a bobbing motion of the head.

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鈥淭his suggests that starlings are actually using multiple regions of the retina, not just the fovea, to look at objects,鈥� says Butler.

It鈥檚 not clear why starlings do this. However, it may be significant that starling retinas are unusually variable in their sensitivity. There is a fovea, but across the rest of the retina the density of the light-sensitive photoreceptors over distances of a few tenths of a millimetre. By bobbing their heads, the starlings may be able to quickly integrate the different types of information gathered by the different areas of retina.

Butler says she expects other songbirds probably gaze at objects in the same way. 鈥淭his research really just highlights that we can鈥檛 make human-like assumptions about how birds look at their world,鈥� she says.