The Comparison Of Diets Of Owl Essay

, Research Paper

Comparing the Feeding Habits of Barn Owls and Screech Owls

Background

Owls are comprised of two closely related households in the avian order Strigiformes-the barn bird of Minerva, or Tytonidae, and the typical bird of Minerva, or Strigidae. Owls are comparatively big birds, with a large caput and short cervix, a aquiline beak, talons adapted to prehend quarry, and soft, heavy feather adapted for Swift yet about soundless flight. Owls have big eyes located on the forepart of their face. The eyes are about fixed in their sockets, so that the full caput must be rotated or bobbed for the regard to be shifted and for distance to be assessed.

Owls have first-class hearing and really big ears, although these are covered by plumes and are non readily seen. The ears are placed unsymmetrically on the caput to assistance in observing the location of distant, about soundless quarry. Their sense of hearing is likely besides aided by their facial disc, which helps to concentrate sound moving ridges onto the ears. An bird of Minerva & # 8217 ; s sense of hearing is so acute that it can accurately strike its quarry in entire darkness, following the squeaks and rustling sounds created by a little mammal in gesture.

The sex of an bird of Minerva is non easy to separate, although typically, female bird of Minerva are larger than males. Owls Begin to incubate their eggs as they are laid. When hatching occurs it is consecutive, and different-sized immature are in the nest at the same clip. During old ages when quarry is comparatively abundant, all of the immature will hold plenty to eat and may last. In leaner old ages, nevertheless, merely the largest immature may be fed adequately.

( Egan, T. ( 1994 ) . Oregon, Foiling Forecasters, Thrives as it protects owls. New York Times, October 11, pg A1, A19 )

Most bird of Minervas are nocturnal marauders, largely feeding on little mammals and birds, and sometimes on little reptilians, toads, larger insects, and angleworms. A few specialised bird of Minervas feed on fish. Owls are known to alter their nutrient penchant, depending on local or seasonal handiness. Most owls do non digest the pelt, plumes, or castanetss of their quarry, and they regurgitate these points as pellets, which can be collected at roosts and examined to larn about the eating wonts of these birds.

Barn bird of Minerva

The barn bird of Minerva are a distinctive-looking group, with a characteristic like facial disc of stiff, white plumes, dark eyes, long legs that separate them from typical bird of Minerva. All barn bird of Minervas are nocturnal marauders, and their quarry consists largely of little mammals. There are nine species of barn bird of Minerva ( genus Tyto ) and two species of closely related grass bird of Minerva ( genus Phodilus ) .

The most familiar species is the barn bird of Minerva ( Tyto alba ) . The barn bird of Minerva is one of the most widely distributed species of birds, happening on all continents except Antarctica. The barn bird of Minerva is the lone representative of this household in the Americas, happening uncommonly through most of the United States and in much of Central and South America. The barn bird of Minerva nests in pits in trees and in barns and abandoned edifices, and it hunts at twilight and at dark over fens, prairies, Fieldss, and farmyards.

Screech Owl

The screech-owl ( Otus kennicotti ) is a comparatively familiar species in forests of temperate parts. This 8.5 & # 8243 ; ( 22 centimeter ) long species occurs in several colour phases-grey, ruddy, and brown-and it nests in pits and sometimes nestboxes.

Owl Pellets

The mean owl pellet contains castanetss and other non-digestible points such as hair and plumes. After the bird has eaten its quarry ; the quarry is digested into the ventriculus where grinding occurs. After crunching the bird & # 8217 ; s ventriculus makes a ball of the indigestible stuff, is expelled by oral cavity. An mean bird of Minerva can bring forth an norm of one to two pellets a twenty-four hours.

John Day, Oregon

The John Day country is considered a semi-arid desert part. John Day, Oregon is located at Latitude 44.418427 and Longitude -118.949399, which is 125 stat mis south of Pendleton, Oregon in Eastern Oregon. A desert is an waterless land country, one that loses more H2O through vaporization, than it additions through precipitation-rain, sleet, or snow. These countries by and large receive fewer than 10 in ( 250 millimeter ) of H2O yearly. Average one-year precipitation in the universes comeuppances scopes from about 0.4-1 in ( 10-25 millimeter ) in the driest countries to 10 in ( 250 millimeter ) in semiarid parts. The term desert can besides be defined by comparing the solar energy an country receives with the its one-year precipitation

Desert animate beings

The many animate beings that have adapted to harsh desert life include insects, arachnoids, reptilians, birds, and mammals. Unlike workss, these animate beings can seek shelter from the searing Sun, firing cold, and strong air currents by creeping into belowground tunnels. Reptiles, whose organic structure temperature is controlled by the temperature of their environment, travel between sunshine and shadiness to remain cool. Birds, utilize metabolic H2O, behavioural versions, active at twenty-four hours or cool parts of the twenty-four hours, may be mobile and they may migrate during the harsher seasons.

Merely as the seeds of desert annuals can remain hibernating for decennaries, so can those of egg-laying desert animate beings. Amphibians and freshwater runt hatch, mature, mate, and put their ain eggs rapid sequence in desert pools created by infrequent storms.

Some little mammals, such as gnawers, excrete merely concentrated urine and dry fecal matters, and perspire small as a manner of conserving organic structure fluids. Desert insects protect themselves from hot dry conditions with a waxy coating, long legs that maintain them elevated above the hot land, and virtually moistureless eliminations. ( Watkins, T.H. ( 1995 ) . Desert Extraordinare. Audubon 97: 44-54. )

My inquiry is how make the Western Screech-owls and the Barn-owls diets compare. Both unrecorded in John Day part of Eastern Oregon, which make the same assortment and sum of quarry available to both of the bird of Minerva. I hypothesis that their diet will be really similar if non the same due to the same assortment of quarry that live in John Day Oregon. Both of the bird of Minervas have similar eating wonts that include quarries like Vole, mice, birds and occasional serpents. I will compare a survey done by Hancock Field Station in John Day Oregon on the types of nutrient that the Barn-owl chows in conformity to what they find in the bird of Minerva pellets verses what I find in five Western Screech-owl pellets.

When I looked at the castanetss in the five different Screech bird of Minerva pellets, I was able to see what sort of animate beings they were from and therefore utilize these consequences against the consequences of the Barn owl prove done at Hancock Field Station. Comparing these two sets of informations will assist me reply my inquiry of how the diets of Screech bird of Minerva and Barn owls compare.

Materials and Methods

To happen out how the Barn bird of Minerva and the Western Screech-owl & # 8217 ; s diets compare I collected owl pellets to happen out what the bird of Minerva are eating. I located Western Screech-owl pellets, but was non able to obtain any Barn bird of Minerva pellets from Eastern Oregon. In stead of Barn owl pellets, I located a survey done by the Hancock Field station in John Day refering the eating wonts of Barn owls. I so collected five Screech bird of Minerva pellets to dissect. When I finish dissecting the Western Screech-owl pellets I will hopefully be able to happen out the mean diet of a Western Screech-owl.

To happen out what the bird of Minerva & # 8217 ; diet utilizing the bird of Minerva pellet, the pellet must be dissected and the different castanetss and skulls examined. I used a dental choice and a brace of pincers to divide the hair and plumes from the castanetss and skulls. Once all castanetss were separated from the hair, I identified animate beings by utilizing size of bone, colour of dentitions, size of skull, and what sort of stuff surrounds the castanetss ( i.e. hair or plumes. ) Once the castanetss were identified I determined what type of animate being. Using this technique on all five Western Screech-owl pellets I was able to acquire an indicant of what the Western Screech-owl & # 8217 ; s.

Consequences

The consequences I got were similar to the consequences the Hancock Field Station found on their experiment with Barn bird of Minerva. When my survey of the bird of Minerva 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 bird of Minerva in the pellets I identified all the castanetss that were present and came up with a decision.

In pellet one I removed the followers:

Number of Bones Type of Bones

1 Skull

/ & gt ;

2 Pelvis Boness

2 Tibia with Fibula

2 Humerus

5 Lumbar Vertebrae

3 Thoracic Vertebrae

2 Cervical Vertebrae

6 Ribs

1 Xiphisternum

A manner you can state that this animate being is a gnawer is by the animate being & # 8217 ; s teeth being orange. Orange teeth are alone to gnawers and gnawers merely. This animate being besides had a smaller thirster and stouter skull, which ruled out Moles, Shrews and Voles.

In pellet two I removed the followers:

Number of Bones Type of Bones

1 Skull

1 Tibula with Fibula and Femer

2 Pelvis Boness

1 Radius Ulna

6 Lumber Vertebrae

1 Sacrum

2 Humerus

1 Femur

2 Cervical Vertebrae

3 Thoracic Vertebrae

4 Ribs

1 Radius with ulna

This animate being besides had orange dentitions, but the skull was longer and dilutant. This ruled out a mouse and the orange dentition ruled out moles and termagants. The castanetss were besides bigger than a mouse so my decision was it was a Vole.

In pellet three I removed the followers:

Number of Bones Type of Bones

1 Keel

1 Tarsometatarus with Digits

1 Sternum

1 Tibiotarsus with Fibula and Femur

1 Claricle

1 Tibula

1 Femur

2 Wrist

1 Ulna with Radius

This pellet had no skull but had a talon and a keel, which made it a bird. There were different castanetss found in this pellet than any other pellet. The different castanetss included Claricle, Carpus, Tibiotarsus, Tarsometatarus and a Keel. These castanetss ruled out any other animate being other than a bird.

In pellet four I removed the followers:

Number of Bones Type of Bones

1 Skull

2 Tibula with Fibula and Metatarsal

1 Pelvis Boness

1 Metacarpals

1 Tail

2 Femur

2 Humerus

2 Radius with Ulna

1 Tibia with Fibula

1 Scapula

4 Lumbar Vertebrae

5 Ribs

1 Thoracic Vertebrae

The animate being in this pellet had a midst and long skull with orange dentitions. It besides had a longer tail with both pess. The orange dentition made it a gnawer and the size and form of the skull ruled out a Mole, Shrew and a Vole. After careful analysis of the castanetss and the skull I determined that the animate being whose castanetss were in this pellet was a mouse.

In pellet five I removed the followers:

Number of Bones Type of Bones

1 Skull

2 Tibia with Fibula

2 Pelvis Boness

2 Humerus

2 Femur

3 Lumbar Vertebrae

1 Sacrum

1 Thoracic Vertebrae

2 Cervical Vertebrae

4 Ribs

1 Radius Ulna

This animate being besides had orange dentitions, but the skull was longer and dilutant. This ruled out a mouse and the orange dentition ruled out moles and termagants. The castanetss were besides bigger than a mouse so my decision was it was a Vole.

When I finished placing all the castanetss I wanted to acquire a full count of what I found and how many of a idiot type of bone I found. The undermentioned chart is all my informations combined.

Number of Bones Type of Bones

4 Skull

2 Tibula with Fibula and Metatarsal

7 Pelvis Boness

1 Metacarpals

1 Tail

6 Femur

8 Humerus

4 Radius with Ulna

3 Tibia with Fibula

1 Scapula

12 Lumbar Vertebrae

19 Ribs

10 Thoracic Vertebrae

6 Keel

1 Tarsometatarus with Digits

1 Sternum

1 Tibiotarsus with Fibula and Femur

1 Claricle

1 Tibula

2 Wrist

1 Ulna with Radius

The Hancock Field Station surveyed 1,000 Barn-owl pellets. After dissecting them in the same manner I dissected the Western Screech-owl pellets they came up with the following informations:

Type of Animal Number of Animals

Vole 562

Mouse 284

Bird 154

( Hancock Field Station ( 1999 ) A Survey in the Eating Habits of Barn-owls. Not Published )

After close rating of this information I came up with the ratio of 4:2:1 with Vole, mouse and bird severally. After I evaluated the informations given to me by Hancock Field Station I compared it to my ratio of 2:2:1 with Vole, mouse and bird severally. I used my ratio against the ratio I got from Hancock Field Station and used it in a eventuality tabular array. A eventuality tabular array is similar to a chi-square analysis, but expected informations is non required. Data is collected on two properties of the elements in a survey. When I entered my informations into a computing machine I got G = 0.707, P = 1.14, df = 5 which means that the two samples are non statistically different.

Discussion

When I began this experiment I wanted to cognize if the diet of Barn-owls and Western Screech-owl which both live in similar topographic points. I hypothesized that they would be similar because of the similar eating wonts of both Barn-owls and Western Screech-owls. I found that my consequences supported my hypothesis. The consequences I got were a 2:2:1 ratio with Vole, mice and birds respectfully. They compared to the trial done by Hancock Field station with the Barn bird of Minerva ; their consequences were a 4:2:1 ratio with Vole, mice and birds respectfully. My consequences do non to the full reflect the eating wonts of Screech owls that unrecorded in John Day. Due to the deficiency of bird of Minerva pellets, I was non able to acquire a full representation of what Western Screech-owls eat. To to the full stand for the eating wonts of the Screech bird of Minerva, I would necessitate 200-300 pellets.

This survey is of import to happen out what the bird of Minerva in John Day Oregon eat. The consequences I got showed what the Western Screech-owls eat verses what the Barn-owls eat. Scientists need to cognize this to see if there is adequate quarry in John Day to back up both the Screech and Barn owl population. If there is a deficiency of quarry there would be competition between Barn and Screech bird of Minerva, and that might take to a lessening of one type of bird of Minerva in John Day Oregon. If there was a lessening in the owl population in John Day, it could perchance throw off the whole ecosystem in non merely John Day but besides all of Eastern Oregon. So cognizing what the Barn bird of Minerva eats verses what the Screech bird of Minerva chows is imperative in maintaining non merely the prey population but besides the ecosystem in Eastern Oregon where it should be. Ecosystems and communities within a idiot system take 100s of 1000s of old ages to develop. But if one animate being becomes nonextant due to the fact that it has to many marauders, the branchings of the animate being & # 8217 ; s extinction could last for 100s of 1000s of old ages. So it is of import to cognize how many marauders a idiot animate being has so you can do certain there is adequate quarry for the marauders. If you run out of quarry, the marauder starts to decease off and a whole prostration of the nutrient web happens and it has a immense consequence on the whole ecosystem.

Some failings that occurred in my experiment were a deficiency of Western Screech-owl pellets. Some other failings might be the truth of the Hancock Field station experiment affecting the eating of Barn bird of Minerva. To to the full acquire an accurate consequence in this experiment I would necessitate to roll up 200-300 pellets from the Barn Owl and the Western Screech-owl. I would necessitate to do certain that the pellets were gathered in the same country during the same clip.

I conclude that the feeding wonts of the Screech bird of Minerva and the Barn bird of Minerva are similar, but non precisely the same. Even though they might hold a similar feeding wonts could non be precisely the same. Different Owls provender on different things harmonizing to the owls size, flight velocity and oculus sight. The Barn Owl might eat more mice and Vole seeing how it nests in a barn and non out in the unfastened. The Western Screech-owl might eat more serpents and other outside animate beings. The nesting topographic point effects the eating wonts of Owls as do other factors. I can reason that they are similar, but can ne’er turn out they are the same. Further experimentation would be needed to acquire an perfectly accurate consequence and comparing between the Barn owls feeding wonts and the Screech owls feeding wonts

A limited
time offer!
Save Time On Research and Writing. Hire a Professional to Get Your 100% Plagiarism Free Paper