Have you ever wondered what the world looks like to birds? Well, Swedish scientists have created a camera that will show you. Amongst other things, it has revealed that birds see tree foliage as much more than just a uniform "wall of green."

As is the case with humans, birds' vision is based around the three primary colors of red, green and blue. Unlike us, however, they also perceive light in the ultraviolet spectrum. Working with then-postdoc student Cynthia Tedore, Lund University's Prof. Dan-Eric Nilsson set out to simulate such a visual system.

In order to do so, the university's Lund Vision Group built a computer-aided multispectral camera that's equipped with a number of optical filters. Those filters are mounted on wheels that can be rotated over top of the lens, imitating the vision systems of various animals. For this study, filters were selected to match the color sensitivity of the four types of photoreceptive cone cells found in birds' retinas.

It was found that when imaging dense foliage, the ultraviolet-sensitive visual system created a much higher degree of contrast than is possible for humans – the tops of the leaves appeared to be very light, while their undersides were very dark. Photos taken with (right) and without the system can be seen below.

The scientists believe that this boosts birds' ability to perceive foliage in a three-dimensional manner, thus allowing them to easily navigate through it. By contrast, people tend to see it as being flatter and more impregnable, since green is the color in which contrast is ordinarily the worst.

"We have discovered something that is probably very important for birds, and we continue to reveal how reality appears also to other animals," says Nilsson. "We may have the notion that what we see is the reality, but it's a highly human reality. Other animals live in other realities, and we can now see through their eyes and reveal many secrets."

A paper on the research was recently published in the journal Nature Communications.

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