The Comparison Of Diets Of Owl Essay — страница 2

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desert is an arid land area, one that loses more water through evaporation, than it gains through precipitation-rain, sleet, or snow. These areas generally receive fewer than 10 in (250 mm) of water annually. Average annual precipitation in the worlds deserts ranges from about 0.4-1 in (10-25 mm) in the driest areas to 10 in (250 mm) in semiarid regions. The term desert can also be defined by comparing the solar energy an area receives with the its annual precipitation Desert animals The many animals that have adapted to harsh desert life include insects, arachnids, reptiles, birds, and mammals. Unlike plants, these animals can seek shelter from the scorching sun, burning cold, and strong winds by crawling into underground burrows. Reptiles, whose body temperature is controlled

by the temperature of their environment, travel between sunlight and shade to stay cool. Birds, utilize metabolic water, behavioral adaptations, active at day or cool parts of the day, may be nomadic and they may migrate during the harsher seasons. Just as the seeds of desert annuals can stay dormant for decades, so can those of egg-laying desert animals. Amphibians and freshwater shrimp hatch, mature, mate, and lay their own eggs rapid succession in desert pools created by infrequent storms. Some small mammals, such as rodents, excrete only concentrated urine and dry feces, and perspire little as a way of conserving body fluids. Desert insects protect themselves from hot dry conditions with a waxy coating, long legs that keep them elevated above the hot ground, and virtually

moistureless excretions. (Watkins, T.H. (1995). Desert Extraordinare. Audubon 97: 44-54.) My question is how do the Western Screech-owls and the Barn-owls diets compare. Both live in John Day region of Eastern Oregon, which make the same variety and amount of prey available to both of the owls. I hypothesis that their diet will be very similar if not the same due to the same variety of prey that live in John Day Oregon. Both of the owls have similar feeding habits that include prey like Vole, mice, birds and occasional snakes. I will compare a study done by Hancock Field Station in John Day Oregon on the types of food that the Barn-owl eats in accordance to what they find in the owl pellets verses what I find in five Western Screech-owl pellets. When I looked at the bones in the

five different Screech owl pellets, I was able to see what kind of animals they were from and thus use these results against the results of the Barn owl test done at Hancock Field Station. Comparing these two sets of data will help me answer my question of how the diets of Screech owls and Barn owls compare. Materials and Methods To find out how the Barn owl and the Western Screech-owl’s diets compare I collected owl pellets to find out what the owls are eating. I located Western Screech-owl pellets, but was not able to obtain any Barn owl pellets from Eastern Oregon. In lieu of Barn owl pellets, I located a study done by the Hancock Field station in John Day concerning the eating habits of Barn owls. I then collected five Screech owl pellets to dissect. When I finish

dissecting the Western Screech-owl pellets I will hopefully be able to find out the average diet of a Western Screech-owl. To find out what the owls’ diet using the owl pellet, the pellet must be dissected and the different bones and skulls examined. I used a dental pick and a pair of tweezers to separate the hair and feathers from the bones and skulls. Once all bones were separated from the hair, I identified animals by using size of bone, color of teeth, size of skull, and what kind of material surrounds the bones (i.e. hair or feathers.) Once the bones were identified I determined what type of animal. Using this technique on all five Western Screech-owl pellets I was able to get an indication of what the Western Screech-owl’s. Results The results I got were similar to the

results the Hancock Field Station found on their experiment with Barn owls. When my study of the owl pellets was complete I had two pellets that were mice, two pellets that were Vole and one pellet which was of a bird. When I studied the remains of the owl in the pellets I identified all the bones that were present and came up with a conclusion. In pellet one I removed the following: Number of Bones Type of Bones 1 Skull 2 Pelvis Bones 2 Tibia with Fibula 2 Humerus 5 Lumbar Vertebrae 3 Thoracic Vertebrae 2 Cervical Vertebrae 6 Ribs 1 Xiphisternum A way you can tell that this animal is a rodent is by the animal’s teeth being orange. Orange teeth are unique to rodents and rodents only. This animal also had a smaller longer and stouter skull, which ruled out Moles, Shrews and