Thursday, January 29, 2009

Barred Owls

Earlier this winter I was standing in the drive way chatting with my neighbor when an owl swooped down out from the trees near by and landed on a fence post in my neighbor’s yard. Apparently my neighbor was feeding some resident red squirrels, who had made their home in the covered patio furniture directly under the fence post where the owl was now sitting, so there was no mystery about what he or she was after.

The owl turned out to be a barred owl, Strix varia in the scientific nomenclature. Barred owls are quite common in Maine, they are certainly the ones I hear vocalizing the most. They are permanent residents of the state, meaning they do not migrate. They are generally permanent residents of their breeding grounds as well, so if you have barred owls around your house it is likely that they will remain. Most owls are active at night, called nocturnal, or during dusk and dawn, called crepuscular. The barred owl is active during all of these times, but may also be active during the day, especially if it is an overcast gray day, as it was the day I saw one on the fence post.

The barred owl is exquisitely adapted to do what it does, which is hunt silently and effectively, preying on small rodents and other animals. All animals have adaptations that allow them to fill their niches, some more so than others. On one end of the spectrum are animals (and plants too for that matter) that are rather cosmopolitan , with very general adaptations that allow them to function and even thrive in a wide variety of conditions and use diverse food sources. Humans, rats, and sea gulls are examples of these wide ranging species. On the other end of the spectrum are plants and animals with very specific or narrow niches—basically they are highly specialized to eat a certain food, be pollinated by just one specific pollinator, or live a certain way. Owls, though they can eat a relatively wide variety of foods, are generally thought to be on the highly specialized end of the spectrum.

The barred owl in my neighborhood, like barred owls all over Maine have their eyes on the front of their faces, like humans. Most other birds have eyes on the sides of their heads. The forward facing eyes do the same thing for owls that they do for us, that is give us excellent depth perception. This helps them hunt during low light conditions. Their ears are also specially adapted to help them hunt after dark. The ears of the barred owl are asymmetric. They have one on each side of their head, like we do, but they are not at the same level, one is higher than the other. This asymmetry helps them pinpoint the location of sounds. Barred owls tend to know their territory very well, so between their good depth perception, their acute hearing and their mental map of every perch in their hunting grounds, they are successful and opportunistic predators.

Pay attention in the next couple of months, Barred owls will be mating, which usually means a lot of vocalization. You may hear their familiar “who cooks for you?” call, or even something that sounds like a pack of monkeys has arrived in the Maine woods. Either way, its more likely that you will hear an owl than see one.

First Aired January 2008