An Analysis of The Differences In The Frequency of Prey Items Caught by Maryland Owls

A Research ProposalMatt Bostick

Background: Owls of Maryland

Five species of owls live in or pass through Maryland.1.Barn owls2.Great Horned owl3.Barred owls4.Eastern Screech owl5.Northern Saw-whet owl

Barred Owl

Adaptations as predators

Owls have special adaptations that enable them to hunt at night.

Large and fixed eyes with binocular vision and good depth perception.

Owls have developed an incredibly flexible neck that allows them to turn their head 270 degrees in both directions.

Their eyes are also extremely light sensitive, allowing them to see well at night.

Barred Owl

Owls as predators

Owls rely on silent flight to surprise their prey.

The shape of the owl’s flight feathers muffles the sound wind makes as it flows past them. Saw-Whet Owl

An idealized food pyramid

Owl Pellets – What Are They?

Owls do not have teeth for grinding and cannot pass whole bone and claws through their digestive tract safely.

The protein enzymes and strong acids that occur in the digestive tract of raptors do not digest the entire meal. The relatively weak stomach muscles of the bird form the undigested fur, bones, feather etc. into a bolus (or wet slimy pellets).

The undigested portions may include beaks, claws, scales, or insect exoskeletons.

Purpose: To analyze the frequency of

prey items caught by the 5 species of owls common to Maryland

To determine if the frequency of prey items is significantly different between the species observed.

Owl PelletsI examine owl 3 owl pellets from each species in order to estimate the frequency of prey items eaten.

Species diversity has two components:

4%

6%

8%

14%

17%

18%

33%

7. Bird

6. Rat

5. Gopher

4. Squirrel

3. Mouse

2. Vole

1. Shrew

1. Species richness: how many different species are present in a habitat

2. Relative Frequency: total number of individuals of each species present given in %

HypothesisI hypothesize that the frequency of prey items found in the owl pellets will be significantly different between species.

Materials I need:

3 Owl Pellets from each species

Dissecting Pan Forceps Probe Metric Ruler Bone Identification

Sheets Gloves

Common Name

Genus Freq Found

Vole Microtus 70%

Shrew Sorex 20%

Mole Scapanus 5%

Deer Mouse

Peromyscus 2%

House mouse

Mus 2%

Rat Rattus 1%

(small bird)

Hirundo rare

Methods- Bone Sorting Chart

Type and # of bones

Vole Shrew Mole Rat Mice Bird

Skulls

Jaws

Shoulder blade

Front legs

Hips

Hind legs

Assorted ribs

Assorted vertebrae

# of animals

Chi-Square

is a statistical test used to determine whether your experimentally observed results are consistent with your hypothesis.

When using chi-square in biology, there is some vocabulary we must know:Hypothesis = a proposed explanation of

an observed phenomenon

Observed results = what you can observe during the course of an experiment

Expected results = what you expect to see based on your hypothesis (predictions)

Our final formula:

X2 = chi-square(o - e) = observed minus expected [sometimes you may see this represented with a d which

means the difference between the expected and observed results]

e = expected resultso = observed results

and = sum of

The formula includes:The formula includes:

)(2)(2

eeox

I will use a table to assist in my data organization.

Species of OwlObserved

VolesExpected

VolesO-E (O-E)2 (O-E)2

E

Great Horned 6 4 2 4 1

Screech 5 4 1 1 0.25

Barn 1 4 -3 6 1.5

Chi – Square Critical Values

Expected ResultsI expect that the results from my chi-square analysis will indicate that significant differences in the frequency of prey items will exist between the 5 owl species studied.