Eyes Manage Glare

an orange and blue kingfisher sits on a tree branch against a blurry background

Biological Strategy

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Image: Vincent van Zalinge / Unsplash / Free non-commercial use

Protect From Light

Access to sunlight is crucial to living systems because it’s the primary energy source for life. However, too much sunlight in the form of ultraviolet radiation (UV) can cause damage to living tissues. Therefore, living systems have strategies to filter out some or all UV radiation. For example, some plants that live in areas exposed to long periods of direct sunlight have reflective surfaces (such as white hairs or powder) that reflect UV light.

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Sense Light (Visible Spectrum) From the Environment

Living systems constantly receive signals from their environment that help them survive. Light (in the visible spectrum) can come from other living systems (such as fireflies) or from non-living sources (such as the sun). Survival often depends on sensing and responding to challenges like low light conditions or light that has been altered in some way. Because basic survival is at stake, living systems must excel at meeting those challenges. A well-known phenomenon is how water bends light. A stork trying to catch a fish underwater can compensate for this bending effect so that when it strikes at the fish, it has a good chance of catching it.

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Birds

Class Aves (“bird”): Eagles, hawks, sparrows, parrots

Birds are evolutionary engineering marvels. They are descended from dinosaurs, but are far from our idea of heavy, scaly reptiles. Of the specific adaptions that set them apart, most notable is flight—although some mammals can fly, birds take the prize for abundance in the skies. Many birds have hollow, lightweight skeletons and specially-designed wings to help them stay aloft. They also have feathers made of keratin that help them stay warm, attract mates, and improve navigation and aerodynamics in flight. In contrast to their dinosaur ancestors, they lack true teeth and have replaced them with specialized beaks and bills.

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Red droplets in the cone cells of kingfisher eyes may allow sight through water or glare by acting as chromatic filters.

Image: Fir0002 / Wikipedia /

Sacred Kingfisher. Taken in Victoria, Australia in November 2008

Image: Alan Wilson /

Belted Kingfisher, Blackie Spit Park, Crescent Beach, British Columbia

“Kingfishers have specialized eyes and excellent eyesight. The retina of each eye has two fovea. The cone cells have a high proportion of red droplets, which may act as chromatic filters, allowing sight through the surface of the water.” (Fowler and Miller 2003: 254)

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