Thursday, January 8, 2015

Why Are Grebe Eyes Red?

This Eared Grebe certainly sports bright red eyes. The photo was taken of a breeding bird at Sand Lake National Wildlife Refuge many years ago.

Why are loon and many grebe eyes red? I remember reading in one of my loon books that, because red is filtered out of water after a depth of 15 feet, the eye would be indistinct to prey. This camouflage may be important, if prey key on eyes of predators. Many creatures make use of an opposite phenomenon—butterflies and moths, for example, often show eye spot patterns on their wings, thus dissuading potential predators, who in turn, do not wish to become prey themselves.

One problem with this hypothesis is that young loons and most young grebes have dark eyes. Other grebes do not even have red eyes, as is the case with many other diving waterfowl. Perhaps red eyes are used to attract mates. That sort of answer is a stock fall-back reply to unanswerable evolutionary questions. A third alternative is that red eyes allow divers to see more clearly under water. The answer many be a combination of all three hypotheses.


  1. That was very interesting. I was reading a book that had a Grebe in it and did a little research. Thanks!!!

  2. The eye color is soo intense. So is there not a specific pigment involved, like carotenoid or something similar? but the red eye is a strucutral color (similar to blue eyes in humans?). Or another theory i had, a strong presence of capillaries in the iris not be responsible too ?