Owl Physiology
Owls have certain physiological advantages that give them an advantage when hunting prey. Owls have the best night vision of all birds of prey. In addition to having excellent vision, their hearing aids in nighttime hunting. Their wings have also evolved to produce a near silent flight, allowing them to sneak up on prey.
Owl Vision
Being nocturnal, owls need the ability to see in the dark. They have developed excellent vision that adapts to the amount of light they are in. This means they have exceptional vision during the day as well as during the night. The basic structure of an owl’s eye is like a human’s. It is comprised of a cornea, a pupil, an iris, a lens, and a retina. The major difference that gives an owl nighttime vision is the concentration light-sensitive rods in the retina. The retina is made of rods and cones, each serving a different purpose. Rods are designed for low-light environments and cones are better suited for high light environments (Scholz, 2001, p. 3).
The iris can expand or contract, depending on the amount of light, giving owls the ability to see in any amount of light. During the day the iris contracts, causing the pupil to shrink. Less light passes through the lens and hits the retina. At night, the iris expands, making the pupil larger, which allows more light to pass through the lens. Once through the lens, the light enters the retina. An owl has many more rods than cones, giving owls the ability to convert small amounts of light into an image. This gives them the advantage when hunting at night.
Owls also have a more tubular shaped eye, as shown in Figure 1, compared to the eye of a human. This gives the cornea a larger size proportionally to the overall size of the eye, allowing...
... middle of paper ...
...ility-to-Fly-in-Acoustic-Stealth-Provides-Clues-to-Mitigating-Conventional-Air.pdf
Dobkin, D. S., Ehrlich, P. R., & Wheye, D. (1988). Retrieved from How owls hunt in the dark: https://www.stanford.edu/group/stanfordbirds/text/essays/How_Owls_Hunt.html
Lewis, D. (n.d). Tawny Owl Skeleton [Online image]. Retrieved from http://www.owlpages.com/image.php?image=articles-Owl+Physiology-Skeleton-01
Scholz, F. (2001). Owls. Mechanicsburg, PA: Stackpole Book.
Sieradzki, A. (n.d.). Owl digestive system diagram. [Online image]. Retrieved from http://www.owlpages.com/image.php?image=articles-Owl+Physiology-Digestion-1.5
Winkler, S. (2008, July 14). How can owls fly silently. Retrieved from How Stuff Works: http://science.howstuffworks.com/zoology/owl-fly-silently1.htm
World Owl Trust. (2012). Eyesight. Retrieved from World Owl Trust: http://www.owls.org/Information/eyesight.htm
As Harwood explains in the poem “a lonely child who believed death clean and final, not this obscene”. When the first shot strikes, her naivety is immediately replaced with guilt as she realises the implications of her plan. Her gun falls from her hands symbolically conveying the shock and guilt of her actions. After the child kills the owl, she weeps on her father’s arm, symbolising the loss of the child’s youth and innocence. This is presented in the visual representation by the images of a barn owl and a young girl crying side by side. The owl was part of the girl and symbolised her innocence. When the owl was killed, her childish innocence was taken away. She is then forced to understand and mature from the events taken place. The author uses the metaphor “owl blind” to convey the sadness of the journey to maturity and adult knowledge that has now begun for the protagonist.
The Pacific Northwest is perhaps most commonly known for its awe-inspiring old growth forests that have been gracing the land for hundreds and hundreds of years. The land in British Colombia, Canada, Washington state, Oregon, and parts of Northern California are the only areas in the world where these forests exist. One of the most unique and amazing inhabitants of this age-old forest is the Northern Spotted Owl. The Northern Spotted Owl has been on the endangered species list for over ten years now. The Northern Spotted Owl can only be found in these old growth forests. The northern spotted owl requires many acres old forests to survive, due to its scarce food supply. They are very sensitive to their habitat, and simply cannot survive in any other environment. These owls, as well as the forests have been disappearing at an alarming rate due to the immense logging industry in its area.
The Northern Spotted Owl can only live in old growth environment, it is considered an “indicator species”: The health of the Northern Spotted Owl population indicates the health of the old-growth forest ecosystem. An individual Northern Spotted Owl needs more than 3,000 acres of old growth to survive, because of its scarce food supply. The Northern Spotted Owl is found in the cool, moist woodlands on the Pacific Northwest. The habitat of the Northern Spotted Owl can be described as trees relatively large in diameter in the stand, multi-layered canopy, large tall live trees with cavities, broken tops, mistletoe, or platforms of branches capable of holding accumulated organic matter suitable for use as a nest, dead standing trees and fallen decayed trees to support abundant populations of prey species, especially northern flying squirrels and woodrats.
Most owls are nocturnal birds that are found everywhere in the world. The fossils of the owls’ existence have dated back 54 million years ago. There are 205 different owl species. The owl species are divided into 2 different groups, one known as the barn owl, and the other as the true owls. True owls are more common than barn owls. The picture above shows a burrowing owl, which is a species of true owls. They have round faces where as barn owls have heart shaped faces. Most owls use their binocular vision to hunt prey. Owls have large eyes that set forward on their heads that allow them to have excellent depth perception. Their eyes have several large special cells called rods that are sensitive to low light. Their eyes are fixed in their
direction, the major problem for their decline would have to be remedied – loss. of the habitat of the sailor. This fact combined with the owls' short life expectancy and late age. breeding only exacerbates the problem. When loggers remove old growth owl loses habitat for its food, housing, as well as protection from predators.
Feathers are complex, branched, keratinized epidermal features commonly associated with Class Aves, or birds (Bock, 2000). Cells in the epidermis called keratinocytes are the structural components of feathers; however, the protein keratin varies in its distribution and can be of different types (Prum, 2002). Many functions involved with feathers include thermal insulation, flight, cleaning of plumage, heat protection, sound production, chemical defenses, water repulsion of plumage, social communication, streamlining the body, and the sensation of touch (Bock, 2000; Prum, 2002). A wide variety of feathers have been characterized. Feathers covering the body are known as contour feathers (Bock, 2000). Contour feathers covering the wings are called remiges, while those covering the tails are called retrices (Bock, 2000). Additional types of feathers include semiplumes, down and powdered down feathers, bristles and semibristles, filoplumes, courtship plumes, and oil gland feathers (Bock, 2000). General characteristics of feathers include the presence of a calamus, which anchors the feather into the bird’s integument (Bock, 2000). Barbs, or closely spaced branches, are attached to the central shaft known as the rachis (Bock, 2000). Barbs on each side of the rachis form a vane (Bock, 2000). Proximal and distal barbules originate from barbs; proximal barbules are near the base of the feather while distal barbules are at the tip of the feather (Bock, 2000; Prum, 2002). When these barbules interlock, the structure of the vane is preserved (Bock, 2000).
8. Taylor, Dan. 1998. Audubon Society Inspired to Action by Bird Die -offs . 17 Jan. 1998 . E-mail . Available bkus@sunstroke.sdsu.edu
the eyes had densely packed lenses and may have served merely as a light sensitive
The iris acts to control the size of the pupil. In bright light, the iris is dilated in such a way as to reduce the size of the pupil and limit the amount of entering light. In dim light, the iris adjusts its size as to maximize the size of the pupil and increase the amount of incoming light.
Thousands of different types of birds roam the Earth as we know it today, so let’s begin consider the origin of these beings. How had these creatures come to be? What was their original form? The evolution of birds has only recently begun to explode with new information within the last decade (Savile, 1957, p. 212). Birds are unique creatures and inhabit a wide variety of locations, but constant among them is the fact that they came from Archaeopteryx. Over time, three key changes have developed with the bird’s anatomy that makes it a paradigm of evolution.
The large ground finches have a higher curve while the medium ground finches have a smaller head and a tiny beak. The place in which the finches live is what changes their appearances and also the weather helps decide the appearance of these finches.
and the iris which is the colored part of the eye, it regulates the amount of light
Dr. Dr. h.c. Grzimk, Bernhard. “The Penguins.” Animal Life Encyclopedia. Volume 7, Birds I. New York: Van Nostrand Reinhold Company, 1968.
...he cornea is deformed so that its surface is oval instead of spherical. Light rays are distorted at the entrance of the eye. This produces a blurred image and is known as astigmatism. To correct it, glasses are given a nonspherical or cylindrical curvature. Cross-eyes and walleyes are produced when both eyes do not work together because of weakness of the eye muscles.
Neck and beak – *The neck is long and felixble as a result bird is able to rotate its head for reaching food and can see all around. *The jaws are teethless and are produced into beak which are variously modified to pick up food, making nests and preening etc. Skin – *The skin of bird is loose which allows movement of the flight muscles. Limbs –*Forelimbs are modified into wings and are attached closer to center of gravity and farther from head than in other animals. *The wings act as propelling organs for flight. *Hand bones are small, fused, flattened and specialized to manipulate the flight