Owl Adaptations

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My favorite animal has always been the owl. I had never worked with birds at all until I came here to the Florida Keys Wild Bird Center, and upon getting an internship here I figured that could very well change after getting to interact and learn about all of the other awesome birds that we have here. I have to say after three months of working with all sorts of raptors, songbirds and shorebirds I was given a run for my money as I got to know and love all of our residents, but after all of this time, and despite their sassy attitudes, the owls still remain my absolute favorites. This is why I feel it’s necessary to write and share with everyone about the amazing adaptations, behavior and general awesomeness that is the owl. I could write a book on how perfectly owls are evolutionarily evolved, so the brevity of this article will merely skim the surface, and I encourage anyone reading this to continue to learn about these amazing birds!

Most people know that raptors in general are fierce predators, and owls are certainly no exception. To start, their hearing is out of this world. Many owls are nocturnal, so they must employ an amalgamation of heightened senses to compensate for the lack of light while they hunt. One of these heightened senses is hearing. Despite their super hearing abilities, they are not entirely unlike humans when it comes to hearing; they are however more acute at detecting certain frequencies that allow them to hear even the slightest of movements wherever their prey may be below them during flight. The structure and placement of the ears has a lot to do with this adaptation. Many owls’ ears are asymmetrical which allows for a heightened sense of directional hearing. Additionally, the shape of their ears (aka aperture) and the feathers surrounding the face of the bird also influence the effectiveness of an owl’s hearing. Ear and face shapes vary between each species and impact the hearing abilities of the owl, as well the configuration of feathers on their faces. The facial disk (the feathers surrounding the face) essentially funnel sound into the ears and can be altered at will by the bird using their facial muscles to adapt to whatever to detect stimuli.

Despite having heightened hearing abilities, owls still have exceptional eyesight adapted to see at night and from high distances. Anyone who has seen an owl is aware that owl eyes are huge! Owl eyes are forward facing. This configuration provides a wide range of binocular vision (seeing an object with both eyes) meaning they can judge the height, depth, and distance of their field of view fairly well. As most also know, owls can turn their heads around exorcist style and quite literally have eyes in the back of their heads. Owls have specialized spinal columns which allow for movement of the head to rotate 270 degrees left or right from the forward-facing position! This means they can quickly observe the vast majority of their surroundings. Aside from having head swiveling super powers and well positioned eyes, the eyes of nocturnal owls are particularly efficient at collecting and processing light. There is a very large range (as the eyes in general are so big) for pupillary enlargement and constriction. Accompanying the advanced ability for adjustment of light induction into the eye, they have an abundance of rods (light sensitive cells) in the retina of the eye. This means that the eye can finely attune their vision to whatever lighting is being introduced. Finally, owls, like many other animals, have a nictitating membrane. This is a thin tissue membrane (in addition to the normal upper and lower eyelids) that spans diagonally across the eye. The extra lid cleans and protects the eye.

owl-eye

Although there are many other topics that are awesome regarding owls and their abilities (i.e. silent flight, adept maneuvering in the dark, body structure, behavior… etc.) that I could talk about here, I feel that their ability to consume and digest the prey that they so skillfully acquire is an important final one to review. Again, it is well known that owls are raptors, meaning they are predacious. Owl diets vary between species – from the hare and fox eating Eagle Owls, to the small mammal, occasional reptiles, amphibians and insects of screech owl or even to the fish eating Brown (you guessed it) Fish Owl. All of these prey items have bones or hair that are not readily digestible by most creatures. The owl however, has evolutionarily thwarted this issue. They do not have a crop (loose sac in the throat of most birds that serves as a storage unit for food) like the majority of other birds. This means that food is passed directly into their digestive systems, bones and all. Owl digestive systems consist of two parts – the proventriculus (glandular stomach that produces digestive enzymes and acid that begin the breakdown of food) and the ventriculus (aka the muscular stomach, or gizzard which holds back the insoluble parts of the prey like bones and fur). In the gizzard, soft, soluble parts of the prey are ground up by the muscles of the ventriculus and passed along through a digestive tract not un-similar to ours and excreted. The indigestible portions (teeth, bones, hair etc.) remain in the gizzard. Several hours after consumption, the remains will be regurgitated in the form of a pellet – generally signifying the bird is ready to eat again.

physiology_digestive_alan_sieradzki

Owls are amazing animals, and they are highly adapted to what they do. I really thought seeing all of these other cool birds would change my mind a little bit about owls, but my experiences here have just given me a wider range of appreciation for all birds and reinforced my love for owls! Seeing these majestic, aloof creatures up close and getting to observe them eat, drink and even physically interact with me has been an amazing and eye opening experience that I will never forget! Seriously, go watch a documentary or read up on them some more because you will not regret a thing…except for not being an owl probably.

Kelly Otto, Sanctuary Intern, 2016

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