The Majestically Magnificent –OWL
Dr. Shilpa P. Salunke (Modekar).
B.V.Sc & A.H., M VSc.(Veterinary Anatomy and Histology) Ph.D.
The moment ‘Owl’ word is uttered or even heard, an image pops up in front of us, of a bird bearing large, facing round deep sighted eyes adding to their upright stance, large head with forward-facing round eyes, flat facial disc and soft fluffy plumage, they cannot be mistaken for anything else. This magnificent avian is one of the most distinctive-looking birds in the world. In our Indian context in some parts of Indian mythology these owls have been revered and given a place of prestige. Laxmi, the Hindu goddess of money and wealth, rides a Barn owl which is her vehicle (vahana). The owl is known as Stithi Prajna, which translates to being unwavering in its decision. Symbolically this warns the society not to get trapped by the splendor of wealth. This symbolism is an incredible lesson, and one of the many wonderful legends about owls. However there are so many myths, like, owls bring bad luck, these are messengers of withces, if you touch a baby owl, the mother will abandon it, if you eat owl eggs or eyes you gain better sight and even that, an owl hoot to ward off evil. Likewise many other myths are there. But truly speaking, this owl is one of the most magnificent avian, who is not that properly understood. That fascination may come from their odd anatomy, which makes them stand out among other bird species. Worldwide, nearly 159 species in 20 genera are found. They are nocturnal, fly nearly silently. Many anatomical facts, like, the heart-shaped facial disk completely encircling face, bill comparatively long and slender; legs rather long with the middle claw with comb. They having the ability of to rotate the head that far, compared to other avians, adds to the fascination. But this fascinating bird, bears many such magnificent features which are rarely discussed and properly understood. Owls range in size from teeny-tiny to large and imposing. The smallest owl is the elf owl, which is only 06 inch inches tall and weighs 1.5 ounces, same like that of a sparrow and found in the southwestern United States and Mexico. The largest owl is Blakiston’s fish owl, weighing 6 to 8.8 pounds with a wingspan of 6.5 feet, found in Russia, China, and Hokkaido, Japan, and it eats fish, as its name suggests.
It is proven fact that all the owls are subject to the same unique adaptations in eyes, hearing, head rotation, feather structure, digestive system, and hind limb musculature. When it comes to the bodily build, all owls share the same general body plan. Their wings are long and rounded and the tail is short. They bear legs and toes which though are of medium length but are exceptionally strong for the size of a bird. Their toe has needle-sharp, curved talon. The outer toe points rearwards during perching and these are normally directed outward or backward in taking prey, which provide the maximum possible spread of toe. It’s a misconception that owls can turn their necks 360 degrees. The accurate measure is 135 degrees in either direction from facing forward, which is 270 total degrees of movement. Not 360, but certainly nothing to scoff at.This ability is important for the owl because of the immobility of its eyes, and the creature has a number of anatomical adaptations that make it possible. Owls have 14 vertebrae in their necks, double the number for the any other avian. They also have alternative blood carrying routing blood to the head and blood pooling systems to keep blood circulating to and from the brain when neck movements cut off circulation. Other than this, owls have air-cushioned vessel casings so they don’t rupture any blood vessels when snapping their necks around so dramatically and quickly.
The Owl bears a head which is broad and accommodates the exceptionally large eyes which are the most distinctive feature of owls. Instead of the usual ‘disc’-shaped eyes which are normally found in birds, owls have large ‘tubular’-shaped eyes that are held tight within the orbit and are protected by the scleral ossicles, or ‘sclerotic ring’, composed of a series of small interlocking bones that form a bony ring within the sclera. These ‘tubular’ eyes are so large that in some small species of owl they can take up to 50% of the skull area. These are virtually immobile. Remarkable flexibility of the neck compensates for the fixed position of the eyes; an owl can turn its head more than 180° in either direction and can thus look directly backward.
Eyes: The vision is binocular, and depth perception is often enhanced by moving the head away from the central plane. Various owls have only rods in the retina, resulting in an absence of colour differentiation. However bear great visual acuity and light sensitivity. It is assumed and it’s actually a big myth that owls are blind in strong light, but the fact is that their eyes bear the pupils, which operate independently, which can be greatly reduced, and give protection to the sensitive retina and providing better daytime vision than that found in people. These are packed with light-sensitive cells, enable owls to operate in almost total darkness. Though they have extraordinary night vision and far-sightedness, but there’s a drawback, as they are far-sighted, owls can’t see objects up close. For to make up for this, they have small hair-like feathers called as filoplumes, present on their beaks and feet—to feel out their food when hunting. Their eyes have three eyelids, one for blinking, one for sleeping, and one is for keeping their eye “tubes” clean. The most important fact is, owls may have amazing eyes, but it’s their ears that do the real work when hunting. And it’s their apparent imperfections that make them so effective. The ears have a specially designed specially designed auditory system, which makes their ability to hear better almost as if they are hearing in 3D. Owl bear ears, which are large but are surrounded by a ruff of papery feathers that serves to concentrate the sound. The feathers covering the ear opening are lacy and permeable to sound. A movable flap –operculum, on the front margin of the opening is said to perform function as a baffle to focus on the sound and direction, it is directed from. In many owls the relative position of the ear opening is asymmetrical, being above a so-called blind cavity on one side of the head and below it on the other. The asymmetry is thought to be related to the sensitivity of each ear to sounds of various frequencies, which provides the owl with the a better ability to localize sound sources in two planes simultaneously. This adaptation makes some owls, locate and capture prey in total darkness, relying on their ability to localize the rustle of a mouse in leaves and to fly to that spot.
One of the most common misperception about owls, that they have extra vertebrae in their neck that allows them to rotate their heads 270 degrees. But the fact is all birds have more vertebrae in their neck than mammals; owls have fewer vertebrae in their necks than many other birds and yet owls are the only bird that can rotate their heads that far, and the main reason for this is, due to a number of unique adaptations that owls possess, like unique arteries and hollow spaces inside vertebrae, compared with other vertebrates and birds. That is the reason why they get the is ability to look in various directions while keeping the rest of the body motionless. Remarkable auditory system and unique eye pattern, allows them to operate in complete darkness. This unique system allows the owl’s brain to construct an auditory map of space whenever the prey to be located. The individual adaptation that combines to make the owl a superbly designed nocturnal predator and also look at some shared mechanisms and behavior patterns that are crucial to its survival.
When it comes to the plumage of owls, it is is soft, dense, and loose, which even acts and provides owls with insulation against cold. Many owls have erectile tufts of feathers usually called as -“ears” or “horns” above the eyes, these tufts serve to break the round outline of the head, adding to the concealment gained from colour and pattern. The flight feathers upper surfaces of are provided with a nap that makes the flight perfectly noiseless, which allow the owl to hear prey without interference caused by the sound of their flight.
Sound plays an important role for owls, especially in mating and territorial defense. Owl sounds include claps of the wings in flight, snaps of the bill, and a variety of vocalization, along with pitches, timbres, and rhythms unique to each species. However female have higher pitch as compared with male. Their specifications including, camouflage, daytime immobility, and silent flight, contribute in making it difficult not only for owls to see each other but even for their natural enemies and human observers as well. Their sound or rather the deep hoots, chirps, whistles are however is melodious to human ears, though not so very typical song category it belongs like other birds singing ability. Their nocturnal routine majorly involves peaks of activity at dusk and dawn. They leave its secluded roost about dusk and moves to a perch overlooking the hunting area. Posturing by singing owls indicates that they communicate by sight as well as by sound. There is a brief period of song, followed by about half an hour of foraging, then a longer period of song. Most of the darker hours of the night are spent inactively, with a period of alternating singing and hunting just before dawn.
Locomotion- Owls are zygodactyls- having special structure of their feet, bearing two toes (toes two and three) facing forward and two (toes one and four) facing backward. This is what is seen in woodpeckers and parrots, and it is optimal for gripping on prey and branches. Owls are not stuck in this setup, however. They can rotate their fourth toe back and forth, which is why when owls are flying, they have three toes in front and one in back. The typical owl perch is a horizontal branch in a tree. Most owls use their feet only for perching and grasping prey. Contrast to this, the burrowing owls, being terrestrial, can run rapidly over the ground and rarely perch in vegetation., whereas the other catogery, the bay owl are habituated to perches vertically on the trunk of a tree, with the legs reaching sideways, one foot above the other. A get a true grip, owls have the ability to lock their toes around an object so that they don’t need to continually contract their muscles. This let them get maximum grip with minimal effort.
When it comes to nesting, Owls are not great at building their own nests, they however prefer to take over those built by other birds, that to the ones that have been abandoned by crows, hawks, or even squirrels. Some opt to nest in cavities or in the crotch of trees, where they can find shelter. The courtship time is rather tedious, because they have a natural fear of each other in order to mate. Male performs various tricks, called as,sky dance” that involves tricks while flying. It is stated that, mating owls then spend lots of time together, preening their feathers.
In a given season, the number of eggs an owl lays depends on her access to the food. If she gets less supplies, then an owl may not lay a single egg. Whereas it has been studied and ststed that, in a given year, a mother owl could lay anywhere from one to 14 eggs. Different species lay different numbers of eggs. During the incubation period, the mother loses feathers on her belly so that she can put her warm skin directly against the surface of the eggs to keep them even warmer. The baby owls, or owlets, hatch within three to five weeks of the eggs being laid, and will hatch in the order in which they were laid. This is known as ‘asynchronous hatching’typically seen in avains, specifically in owls.
So the available data from various studies reveal that the, owls are the only truly nocturnal avian raptors and have evolved several unique adaptations to perfectly fill this role.
