Some species of small owls have eyes in the back of their heads!
OK, not literally ... but they have dark spots, on the back of their head or neck, that resemble eyes.
It is thought that this adaptation developed to thwart predator attacks from behind. Some predators choose not to attack their prey if the prey is clearly watching them, because the attack would likely fail and the predator would merely use of valuable body energy.
One study (Deppe et al. 2003) found that the presence of eye spots on pygmy-owls seemed to reduce mobbing of the owl by small forest birds.
However,
whether such eye spots might also play other roles is unknown. Perhaps
these owls might also use their eye spots as signals to each other, such as
for territoriality, or mate recognition. In the natural world, it is not
unusual for one adaptation to take on additional uses or benefits.
Literature Cited
Deppe, C., D. Holt, J. Tweksbury, L. Broberg, J. Petersen, and K. Wood. 2003. Effect of northern pygmy-owl (Glaucidium gnoma) eyespots on avian mobbing. The Auk 120(3):765-771.
