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Barn Owl Discovery Guide 20 10 /

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Exploring Prey & Predator Relationships Ideal for K-12 Classrooms, Camps, Home-schools, Scouting groups, and more.

Owl Brand Discovery Kits

Copyrighted Material Š 2010 Owl Brand Discovery Kits an Owl Brand Supply Company business http://www.owlbrandsupply.com All rights reserved. No part of this publication may be reproduced or transmitted in any form for resale purpose or by any means, electronic or mechanical, including photocopy, recording, or any informational storage and retrieval system, without permission in writing from the publisher. Requests to make or copy any part of this publication should be emailed to: Email: info@obdk.com or by mail to: Owl Brand Discovery Kits PO Box 12604 Portland, Oregon 97212 Printed in The United States of America

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Barn Owl Discovery Guide Table of Contents INTRODUCTION TO THE BARN OWL & RELATED SUBJECTS................................................... Page 4 Why Study the Barn Owl?.................................................................... 4 Barn Owl & Vantage Positions........................................................... 5 Nesting & Mating Habits...................................................................... 6 Hunting Techniques................................................................................ 8 Seasonal Prey of the Western Barn Owl....................................... 10 OWL PELLET DISSECTION LAB................................ Page 11 Food Web in Relation to the Barn Owl – Exercise 1.................16 What’s on the Outside? – Exercise 2..............................................15 What’s on the Inside? – Exercise 3..................................................16 Bleaching & Mounting Bones to the Charts – Exercise 4......17 Owl Brand Discovery Kit Bone Identification..............................18 Certificate of Completion................................................................... 25

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Introduction of the Barn Owl & Related Subjects Why study the Barn Owl? Barn Owls (Tyto alba) have been a source of fascination for generations for many reasons. From American Indian stories to Celtic myths, the mysterious habits of the Barn Owl have inspired storytellers worldwide. Perhaps you ventured out into the night and heard the banshee-like cry of a hunting Barn Owl; or maybe you’ve been frightened by a shadow falling across your path, which disappeared as quickly as it appeared. Don’t be alarmed. You have probably been a witness to one of creation’s most interesting nocturnal (night) hunters.

The Barn Owl is found nearly worldwide in countries with moderate climates, plentiful in numbers, useful in rodent population control, and a vital member of our ecosystem. Studies of these owls reveal much information to scientists, biologists, and students alike in areas of food webs and chains, habitat studies, and much more. While Barn Owls are creation’s gifts to farmers because they hunt rodents that harm crops, they are also gifts to the classroom in that they provide an exciting hands-on approach to learning!

One of the most common scientific methods used to study and compare the diets of Barn Owls is owl pellet dissection. Because of the abundance of Barn Owl pellets throughout the world, these are inexpensive educational tools that also contain rich learning opportunities. The Barn Owl’s unique digestive

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Owl Brand Discovery Kits system creates a pellet using undigested portions of its prey.

The pellet is then orally expelled. If you find pellets scattered below a tree, look up carefully, you may see an owl roosting (resting on a fixed horizontal object) or nesting!

Barn Owl & Vantage Positions Barn Owls are originally cavity dwellers. Before the construction of man-made habitats like silos, barns, and church steeples, Barn Owls had to navigate the landscape for a safe and advantageous nesting and roosting site. Sites that lend themselves to prime hunting and safety are referred to as Vantage Positions. Notice in the rock wall to the right the “whitewash.” This is a biologist’s first sign that a Barn Owl may reside here. What makes this type of position extremely ideal for any bird of prey is the way that it sits above an open field or meadow. This field will supply several families of Barn Owls, living in the above rock formation, all year long.

When hiking below these vantage points, keep your eyes on the ground.

If you locate a “Bone yard” you can probably look up and find a nesting site for different species of owls, in this case, a Barn Owl. And if you look around the base of these rocks, you’re likely to find owl pellets, feathers, bones, masses of fur, and more!

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Nesting & Mating Habits of Barn Owls Barn Owls belong to a group of birds known as cavity dwellers. Cavities are defined as holes and caves. When it comes to choosing nesting sites, these owls are not too picky. In a natural setting, they will inhabit tree cavities, crevices between the fronds of palm trees or small caves in cliffs and holes in cut banks. They readily accept artificial cavities as well, and have been found to nest in any snug, quiet enclosure ten feet or more off the ground. These might include rafters, openings between bales of hay, attics and unoccupied rooms in upper stories of buildings. Other suitable nesting sites may be barrels, steel drums, and specially designed nesting boxes.

Barn Owls have a particularly short life span, usually from three to five years. They have a tremendous reproduction capacity. In some regions, they have been known to nest year round, raising as many as four clutches (group of hatched eggs). Barn Owls in the most populated areas of the southwest and northwest United States begin selecting nesting sites in December or January. The nesting season is typically from February to May, with peak hatches in April. Occasionally new nests may be started as late as March. By July, most nest sites have been vacated by the young, who have flown to nearby trees or buildings for the final stages of their development.

A second nest for the season with the same mate may be started in the same or in a different location. The owls may have different mates during subsequent mating seasons. Males may have two concurrent mates nesting as much as a mile apart during a single season if there is a shortage of males in the area. The clutch size varies, and can commonly have as many as eight eggs. As many as 15 eggs have been seen in several nests; and one case in Texas records an extraordinary clutch containing 27 eggs in a single nest box. Even more amazing is that they all survived beyond the juvenile period.

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Owl Brand Discovery Kits The hen (female) lays one egg every two or three days and begins incubating immediately after the first egg is laid. The eggs are incubated for 30 to 33 days each. The chicks hatch in the order in which they were laid, which results in siblings with as much as two weeks age difference between them.

During the incubation period, the female remains on the eggs almost continually. She is fed by the male, but nevertheless, loses much of her stored fat. While nesting, the hen often becomes skittish and restless. During this time she is reluctant to leave the nest unguarded. If she is forced to flee in a state of panic and fear, she may abandon the nest. For this reason, it is wise not to disturb a nesting hen during the early part of the breeding season.

A parent frightened away from the nest after the incubation period will instinctively return to the nest to continue caring for his or her young. However, inspection of the box during the day in April or May will likely as not find the young home alone. The parents will be roosting in a quiet location nearby.

Having worked all night hunting to feed the hungry chicks, they no doubt want some quiet.

While an adult Barn Owl may eat one rodent a night, each chick may eat from two to five, depending on the size of the chick and the size of the rodent. During the course of the breeding season, as many as three thousand rodents and small birds may be consumed by the parents and their family of five young.

If all goes well, young owls will have made their first flight to a nearby tree or building at approximately eight weeks of age. At this stage they begin final preparations for life on their own; mastering their skills of flying and hunting, while learning how to avoid predators like the Great Horned Owl. The parents continue feeding the young for another four to six weeks. At approximately 18 months of age, the young will begin this reproductive process themselves.

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Hunting Techniques of Barn Owls As hunters, Barns Owls are well-adapted creatures. If you are lucky, you might be fortunate enough to see one in flight, but it is doubtful you will hear the flapping of its wings. Unlike the noisy flight of the pheasant, pigeon or duck, their extraordinary light body weight, wingspan, and feathers are unique, designed to render them almost silent in flight. This also allows the owl to keep both tuned in and aligned with the location of its prey as it flies toward it. Mice, shrews, voles, rats, moles, small birds and insects rarely know what hit them when they become the main item on the menu of the Barn Owl. The Barn Owl flies differently when seen hunting during the daylight hours which generally happens only when it is feeding its young.

While many people believe the Barn Owl is blind during the day, it actually has eyes that are well equipped for diurnal (daytime) hunting. The owl has a muscular iris, designed to respond like an automatic shade or curtain, that allows just the right amount of light to pass through the cornea or window of the eye, then through a transparent lens and back onto the retina. They have far better eyesight than humans do. With plenty of light, Barn Owls found hunting during the day are able to locate their prey by sight from great distances, and glide in for the kill.

Their highly developed sense of hearing, thought to be 35 to 100 times more sensitive than our own, allows the Barn Owl to hunt in almost complete darkness. They can hear squeaking, scratching or rustling through the dirt, Compared with other birds of prey, the wing tips of an owl are much softer; this enables it to fly silently.

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Humans use muscles to move their eyeballs. The large eyes of an owl do not move within the eye socket, instead, the owl rotates its head to observe the world around it, as if it were looking through a pair of binoculars.

leaves, or grass, pinpoint the location of that sound in a second, and then align their beak (like an arrow) towards the location of their prey. Taking off from a vantage point, the Barn Owl flaps its wings silently, while swinging its feet back and forth. Then, just before its head collides with the ground and the unsuspecting prey, the owl throws its head back, thrusts its feet forward and sinks its razor sharp talons deep into the body of the prey.

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Seasonal Prey of the Western Barn Owl Depending on the season, the Barn Owl can have a very diverse diet. Pellets collected in various seasons will produce the bones of some of the animals shown below. There are some animals, such as small rodents, that are present in the diet all year long but other migratory animals and insects only present themselves are prey during certain times of the year. Many of these prey are pests to farmers so the Barn Owl is a welcome member of most farming communities as they are a natural form of pest control.

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NOTES:

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Owl Pellet Dissection Lab Barn Owl pellets have been chosen because these owls swallow small rodents and birds whole, and the resulting pellets generally contain the complete skeletons of their prey. Pellets begin forming within the digestive tract of an owl as soon as the prey is swallowed. Enzymatic juices break down the body tissues in the prey but leave the bony materials and hair or feathers undigested. Depending upon the prey eaten, the undigested portions may include beaks, claws, scales, or insect exoskeletons. This type of material has little nutritional value and must be “gagged” from the system.

Predatory mammals such as bobcats and wolves have teeth to grind up bones and claws, and a digestive tract adapted to pass these ground parts. Owls, on the other hand, do not have teeth for grinding and cannot pass whole bone and claws through their digestive tract safely.

Instead, these materials form a pellet that is surrounded with the hair or feathers of the prey consumed. The pellet is then orally expelled, or gagged, and the owl begins feeding again.

You will need the following items in order to conduct a Barn Owl Discovery Kit Pellet Lab: OBDK Bone Identification Charts Pencil Clean sheet of paper Two probes Tweezers Magnifying glass Paper towels Antibacterial wipes White glue Tub of water diluted bleach

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To aid in prey identification To record findings To place extracted bones on To loosen fur from bones To extract bones away from fur To identify bone type To absorb excess water To sanitize work station To secure bleached bones to bone chart To whiten extracted bones

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Owl Brand Discovery Kits Scientists and teachers take advantage of this unique process by collecting these pellets and examining their contents. Since owls are not very selective feeders, these pellets can be used in a variety of instructional settings. The contents are a direct indication of what an owl has fed on. A one-year study of a particular Barn Owl revealed the following diet: 1,407 mice, 143 rats, 7 bats, 5 young rabbits, 375 house sparrows, 23 starlings, 54 other birds, 2 lizards, 174 frogs, 25 moths, and 52 crickets.

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Constructing a Food Web Animals that eat other organisms for energy and growth are called consumers. There are three consumer levels found in a food web, primary, secondary and tertiary. Primary consumers are usually herbivores; they feed on photosynthetic products such as grass and seeds. Secondary consumers gulp down primary consumers. And tertiary consumers (carnivores) devour secondary consumers and are usually found at the top of the food chain. Here is an example of a food web including the Barn Owl.

Exercise 1:

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What other carnivores and herbivores would you add to the food web?

Listing these others, construct a food web, with the Barn Owl at the top.

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What’s on the Outside?

Before you dissect the pellet, examine the outside of the pellet for clues to where it was gathered. Pellets are collected from a variety of places around the country. Use the chart below to see if you can determine where the Barn Owl might have gagged your pellet.

What you might find: Where owl gagged the pellet: Milo Seeds → Open sheds Grain → Grain elevator Dirt → Cut banks and under trees Hay or Straw → Barns and Hay Sheds Feathers → Man-made nesting boxes Pine needles → Under Evergreen trees

Exercise 2: 1. On your piece of paper, write down the clues that might indicate where your pellet was gathered.

2. Can you identify other items stuck to the outside of the pellet?

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Owl Brand Discovery Kits

What’s on the Inside?

Exercise 3:

Label a clean sheet of paper for each pellet you dissect, for example, pellet one, pellet two, etc.

Note: If you find that the pellets do not come apart easily, you can soak them in warm water to soften them.

Using the probes provided, begin to loosen the hair of the owl pellet. As bones are uncovered, carefully remove them using your tweezers and place them onto a properly labeled sheet of paper.

Take extra care to keep skulls intact and near the mandibles (see Owl Brand Discovery Kit Bone Identification Charts).

Continue to extract bones from the hair of the prey. Once you have found all the bones, you can begin identifying them by comparing them to the illustrations on the charts provided.

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Bleaching & Mounting the Bones to your Owl Brand Bone Identification Charts

Exercise 4: 1.

Keep the bones from each prey item separate by setting each set onto a separate clean (labeled) sheet of paper.

2. Place the bones into a tub of diluted bleach to whiten them.

(Bleaching is Optional) 3. After the bones have been cleaned, set them onto a separate dry paper towel.

4. Using a magnifying glass and the Owl Brand Discovery Kits Bone Identification charts, try to identify the type of skeleton that was found in your owl pellet.

5. Use white glue to attach the bones to the correct Bone Identification chart.

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BIRD

CLAVICLE

MANDIBLE

SKULL (top view) ULNA FEMUR

FIBULA RADIUS TIBIO TARSUS

SCAPULA

PELVIS

HUMERUS

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MOLE

Scaparus orarius

MANDIBLE

CLAVICLE

FIBULA

HUMERUS SKULL (top view)

TIBIA FEMUR PELVIS

SCAPULA

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MOUSE Microtus

CLAVICLE C

SKULL SK (top view) SKULL (side view)

FEMUR

FIBULA

RADIUS

TIBIA

SCAPULA

ULNA

HUMERUS PELVIS

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RAT

Microtus CLAVICLE

SKULL (side view)

FEMUR

FIBULA RADIUS SKULL (top view)

TIBIA

ULNA

HUMERUS

SCAPULA PELVIS

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SHREW

Sorex vagrans

MANDIBLE

CLAVICLE ULNA RADIUS SKULL (top view) (t HUMERUS

TIBIA FIBULA

FEMUR PELVIS SCAPULA

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VOLE

Microtus

CLAVICLE

FIBULA

TIBIA

MANDIBLE SKULL (top view)

RADIUS HUMERUS

ULNA

FEMUR PELVIS SCAPULA

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NOTES:

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Certificate of Completion Recognizes:

Student Name

Date

For the completion of the

Owl Pellet Dissection Lab Teacher

Grade

School

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Conserving Owls: Cause and Effect The conservation of owls is an important part of preserving wildlife but also has many benefits to property owners, ranchers, and farmers. Barn owls face many natural hazards and have a very high mortality rate. It is common to find numerous juveniles that have died below the roost or nesting location of an owl. Constructing and mounting a nesting box eliminates one of these factors and helps with the following: 1. Good stewardship. We are entrusted to be good managers of the planet and all of its inhabitants. Encouraging a specie’s survival is part of that responsibility.

2. Good farming. Each year, the cost of pesticides and controls increase and add expense to efficient farming practices and are not desirable by either the farmer or the consumer. Nesting boxes encourage a strong population of barn owls that prey on rodents, insects, and a variety of other pests that are harmful to crops. Effective barn owl nesting campaigns have been known to lower and even eliminate expensive pest control costs for farmers who employ these measures.

3. Good fun. Building a nesting box is a great project for students, campers, scouts, and every community group wanting to participate in good stewardship. Building a box and finding a good location instills that sense of responsibility in our young people and ensures future generations of stewards of our environment.

Where would I hang a Nesting Box? Barn Owls like to either be hidden from the view of humans and predators and undisturbed. If the owl can hide, it can easily become accustomed to almost any type of regular human activity or noise and often will quietly observe human activity. They seem to prefer perching on wood rather than metal or stone (presumably for comfort and minimum heat loss) and well-used roost places are almost always where the owl can stay completely dry during wet weather. Given a choice of perching places a barn owl almost always perches at least 10 feet above ground level.

Good locations to hang boxes include high in trees on the edge of a hay or open field, in the high reaches of a barn, on the inside of a hay barn or shed, or on the outside of the structure facing the open field.

Good luck!

For more information on nesting boxes or to purchase a wooden nesting box, write to info@ obdk.com.

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Learn about Prey & Predator Relationships with Owl Brand Find additional resources on our website at www.obdk. com. Choose from a selection of books, videos, online guides, and more. Additionally, join Owl Brand Discovery Kits on Facebook by searching for our name and join the community to stay up to date on the most current events and news about the subject of dissecting, teaching, or gathering owl pellets for education.

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Owl Brand Discovery Kits Exploring Prey & Predator Relationships