Owl Pellet Essentials Dissection Lab

Exploring Prey & Predator Relationships

Owl Pellet Dissection Lab

1 Proventriculus

2 Ventriculus (gizzard)

3 Liver

4 Pancreas

5 Intestines

6 Cloaca

7 Vent

8 Kidney

9 Heart

10 Lungs

10

1

8

2

6

7

4

5

3

9

Owl pellets are a product of the unique digestion system of

birds. Owls and other birds cannot chew their food as many

animals do. They have to swallow their smaller prey whole

and tear larger prey into pieces. An owl’s food travels

directly into their digestive system.

Bird stomachs consist of two parts. The first part

is the glandular stomach or proventriculus,

which produces enzymes, acids, and mucus that

begin the process of digestion.

The second part is the muscular stomach,

called the ventriculus, more commonly called

a gizzard. There are no digestive glands in the

gizzard. In birds of prey, the gizzard is useful as a

filter, holding back insoluble items such as bones,

fur, teeth and feathers.

The softer parts of the bird’s diet are ground by

muscular contractions, and allowed to pass through

to the rest of the digestive system, which includes

the small and large intestine. The liver

and pancreas secrete digestive enzymes into

the small intestine where the food is absorbed into

body as energy.

1

2

5

4

3

The Formation of Owl Pellets

© 2011 Owl B r and D i s c ove r y K i t s . A l l r i ght s r e s e r ved . Rep roduc t ion pe rmis s ion f o r educ at ion purpo s e s on l y and not f o r r e s a le o r c ommer c ia l u s e wi thout spec i f i c p e rmis s ion .24

Owl Brand Discovery Kits

1 Proventriculus

2 Ventriculus (gizzard)

3 Liver

4 Pancreas

5 Intestines

6 Cloaca

7 Vent

8 Kidney

9 Heart

10 Lungs

10

1

8

2

6

7

4

5

3

9

Owl pellets are a product of the unique digestion system of

birds. Owls and other birds cannot chew their food as many

animals do. They have to swallow their smaller prey whole

and tear larger prey into pieces. An owl’s food travels

directly into their digestive system.

Bird stomachs consist of two parts. The first part

is the glandular stomach or proventriculus,

which produces enzymes, acids, and mucus that

begin the process of digestion.

The second part is the muscular stomach,

called the ventriculus, more commonly called

a gizzard. There are no digestive glands in the

gizzard. In birds of prey, the gizzard is useful as a

filter, holding back insoluble items such as bones,

fur, teeth and feathers.

The softer parts of the bird’s diet are ground by

muscular contractions, and allowed to pass through

to the rest of the digestive system, which includes

the small and large intestine. The liver

and pancreas secrete digestive enzymes into

the small intestine where the food is absorbed into

body as energy.

1

2

5

4

3

The Formation of Owl Pellets

© 2011 Owl B r and D i s c ove r y K i t s . A l l r i ght s r e s e r ved . Rep roduc t ion pe rmis s ion f o r educ at ion purpo s e s on l y and not f o r r e s a le o r c ommer c ia l u s e wi thout spec i f i c p e rmis s ion . 25


When the owl is ready to gag up the pellet, it will turn

its head at an angle or to the side and open its beak.

Owls will often close their eyes and the facial discs will

narrow. They rarely leave their perch during this

process.

Stretching its neck, the owl’s beak

opens wide and the pellet pops out

with little fanfare.

At the end of the digestive tract (after the large intestine)

is the Cloaca (klo-A-ka), a holding area for Uric acid,

also know as Urea. Urea excretions are the white bird

droppings we see on buildings and below perches. This

form of excretion helps minimize water loss.

The cloaca opens to the outside by means of the

vent.

Several hours after eating, the indigestible

parts (fur, bones, teeth & feathers that are still in

the gizzard) are formed into a pellet the same

shape as the gizzard. This pellet travels up from

the gizzard back to the proventriculus where it can

remain up to ten hours before being gagged up.

1

2

Scientists have concluded that the pellet

remains in the bird’s system until all the

nutrition has been absorbed into the bird’s

system.

How does the Owl Expel the Pellet?

Typically, an owl will not eat more prey until it has

emptied it’s system of the previous meal. If they do

eat more, that food will be compacted into the

previous remains. For that reason, pellets can range

in size from under an inch to as many as four

inches, and contain up to 4 to 5 prey! Owl Pellet





Barn Owl pellets havebeen chosen because theseowlsswallowsmallrodentsandbirds whole, and the resultingpellets generally contain thecompleteskeletonsoftheirprey.Pellets begin forming withinthe digestive tract of an owl assoon as the prey is swallowed.Enzymatic juices break downthebodytissuesinthepreybutleavethebonymaterialsandhairorfeathersundigested.Dependingupon the prey eaten, the undigested portions may include beaks,claws,scales,orinsectexoskeletons.Thistypeofmaterialhaslittlenutritionalvalueandmustbe“gagged”fromthesystem. Predatorymammalssuchasbobcatsandwolveshaveteethtogrindupbonesandclaws,andadigestivetractadaptedtopassthesegroundparts.Owls,ontheotherhand,donothaveteethforgrindingandcannotpasswholeboneandclawsthroughtheirdigestivetractsafely.Instead,thesematerialsformapelletthatissurroundedwiththehairorfeathersofthepreyconsumed.Thepelletisthenorallyexpelled,orgagged,andtheowlbeginsfeedingagain.

You will need the following items in order to conduct a Barn Owl Discovery Kit Pellet Lab:

OBDKBoneIdentificationCharts ToaidinpreyidentificationPencil TorecordfindingsCleansheetofpaper ToplaceextractedbonesonTwoprobes ToloosenfurfrombonesTweezers ToextractbonesawayfromfurMagnifyingglass ToidentifybonetypePapertowels ToabsorbexcesswaterAntibacterialwipes TosanitizeworkstationWhiteglue TosecurebleachedbonestobonechartTubofwaterdilutedbleach Towhitenextractedbones

Owl Pellet Dissection Lab



Scientistsandteacherstakeadvantageofthisuniqueprocessbycollectingthesepelletsandexaminingtheircontents.Sinceowlsarenotveryselectivefeeders,thesepelletscanbeusedinavarietyofinstructionalsettings.Thecontentsareadirectindicationofwhatanowlhasfedon.Aone-yearstudyofaparticularBarnOwlrevealedthefollowingdiet:1,407mice,143rats,7bats,5youngrabbits,375housesparrows,23starlings,54otherbirds,2lizards,174frogs,25moths,and52crickets.



Constructing a Food Web

Animalsthateatotherorganismsforenergyandgrowtharecalledconsumers.Therearethreeconsumerlevelsfoundinafoodweb:primary,secondaryandtertiary.Primaryconsumersareusu-allyherbivores;theyfeedonphotosyntheticproductssuchasgrassand seeds. Secondary consumers gulp down primary consumers.And tertiaryconsumers (carnivores)devoursecondaryconsumersandareusuallyfoundatthetopofthefoodchain.HereisanexampleofafoodwebincludingtheBarnOwl.

ExErCisE 1: Whatothercarnivoresandherbivoreswouldyouaddtothefoodweb?

Listingtheseothers,constructafoodweb,withtheBarnOwlatthetop.



What’s on the Outside? Beforeyoudissectthepellet,examinetheoutsideofthepel-let forclues towhere itwasgathered.Pelletsarecollected fromavarietyofplacesaroundthecountry.UsethechartbelowtoseeifyoucandeterminewheretheBarnOwlmighthavegaggedyourpellet.

What you might find:

MiloSeeds→

Grain→

Dirt→

HayorStraw→

Feathers→

Pineneedles→

Where owl gagged the pellet:

Opensheds

Grainelevator

Cutbanksandundertrees

Barnsandhaysheds

Man-madenestingboxes

Underevergreentrees

ExErCisE 2:1.Onyourpieceofpaper,writedownthecluesthatmightindicatewhereyourpelletwasgathered.

2.Canyouidentifyotheritemsstucktotheoutsideofthepellet?



ExErCisE 3: Labelacleansheetofpaperforeachpelletyoudissect,forexample,pelletone,pellettwo,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 pro-vided,begintoloosenthehairoftheowlpellet.Asbonesareun-covered, carefully remove themusing your tweezers and placethem onto a properly labeledsheetofpaper. Take extra care to keepskulls intactandnearthemandi-bles(seeOwlBrandDiscoveryKitBoneIdentificationCharts). Continuetoextractbonesfromthehairof theprey.Onceyouhave foundall thebones,youcanbegin identifying thembycomparingthemtotheillustrationsonthechartsprovided.

What’s on the inside?



ExErCisE 4:

1. Keepthebonesfromeachpreyitemseparatebysetting eachsetontoaseparateclean(labeled)sheetofpaper.2. Placethebonesintoatubofdilutedbleachtowhitenthem.(BleachingisOptional)3. Aftertheboneshavebeencleaned,setthemontoaseparatedrypapertowel.4. UsingamagnifyingglassandtheOwlBrandDiscoveryKitsBoneIdentificationCharts,trytoidentifythetypeofskeletonthatwasfoundinyourowlpellet.5. UsewhitegluetoattachthebonestothecorrectBoneIdentificationChart.

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



CLAVICLE

SKULL(top view)

FEMUR

SCAPULA PELVIS

HUMERUS

TIBIO TARSUS

FIBULA

MANDIBLE

ULNA

RADIUS

BIRD



MOLEScaparus orarius

MANDIBLE

SKULL(top view)

FEMUR

PELVIS

HUMERUS

SCAPULA

CLAVICLE

FIBULA

TIBIA



MOUSEMicrotus

FEMUR

SCAPULA

CLAVICLE

PELVIS

SKULL(top view)

HUMERUS

RADIUS

ULNA

FIBULA

TIBIA

SKULL(side view)



RATMicrotus

SKULL(side view)

SKULL(top view)

FEMUR

PELVIS

HUMERUSSCAPULA

CLAVICLE

FIBULA

TIBIA

RADIUS

ULNA



SHREWSorex vagrans

MANDIBLE

SKULL(top view)

FEMUR

PELVIS

HUMERUS

SCAPULA

CLAVICLE

RADIUS

ULNA

FIBULA

TIBIA



VOLEMicrotus

MANDIBLE

SKULL(top view)

FEMUR

PELVIS

HUMERUS

SCAPULA

CLAVICLE

RADIUS

ULNA

FIBULA

TIBIA



NOTES:

Recognizes:

Student Name Date

For the completion of the Owl Pellet Dissection Lab

Teacher Grade

School

www.obdk.com


Owl Pellet Essentials Guidefor Teachers and Students.

Education is not for the timid.Itisrarelytheimpartationofourknowledgeoracitationofourcre-dentials, although we each aretemptedtochoosethatapproach.Morecommonly,effectiveeduca-tion is the ability to inspire andengageour students andcompelthemtobecomeanactualpartofthestory.Theetymologyofedu-cation includes expressions ofbreeding and rearing up; earlyformsof education, beforewrit-ten word, involved imitation asacentral toolofpassingknowl-edgetofuturegenerations.

At Owl Brand, we want to celebrate those who we think do it well.

Beinganeducatorrequiressomethingfromeachofusthattranscendscultures,fashion,trends,andinsteadembracesthetime-lessskillofstorytelling.Whenstoriesaretoldwithdistincttraitsof

humility,contagiousenthusiasm,andapurposefulresult–amoral,thestorycanbecomealifelessonthatremainsinourconsciousness.

When I first met authorsand sisters, Gail McDiarmid andMarilynMcGee, Iknewtheysharedour concern for the complex issuesfacingourfutureineffectiveecologystewardship.Imetthemthroughthe

Proudly Presents:Running For Home

Running Homefor

Can you find the hidden animals in this book,

including the twoon this cover?

by Gail McDiarmid & Marilyn McGeeIllustrated by Durwood Coffey

“The howling of the windis the voice of my brothers.”Author Unknown

for

introductionoftheirengagingbooktitledRunning for Home.Thatintroductionresultedinaninvitationtopresentatthe2013SummerCelebrationweco-hosteachsummerinIdaho.

They traveled from the across the country to IdahowheretheirgoalwastopresentRunningforHome,abookthattacklesthestoryofecologythroughlovablecharactersChinookthewolf,Wapitithe elk and the hilarious raven Mochni.Theoutcomewasmyoutrightadoptionoftheirimportantmessageandtheirconta-giousenthusiasm.

I’mexcitedthatGailandMarilynwill return to help us reachmore chil-dren with their great message and funstyleofteaching,inescapablycentralinthebook.

I’msoprivilegedtorecommendthisfantasticbook.GailandMarilynweresoverykindtoletOwlBrandparticipateintheircre-ativejourneythroughthetalentsofourgraphicartistandfriendofecology,DavidWinfield.Thestoryiscompelling,butjustasimpor-tant,thesesistersworkwithadepthofcompassionandconviction---not just for thereal lifesubjectsdepictedby theircharactersbutalsofortheaudience.

Whenawell-toldstoryandyoungmindscometogether,theresultcanbeprofound.That’saninvestmentIcangetexcitedabout.

Ihopeyou’llconsideritforyourclassroom.

HappyReading!

Chris

3

“Wapiti!” screams the elk’s mother as she runs to her son. Suddenly, the ground collapses beneath his spindly legs and Wapiti plunges into the raging river. Gasping for breath, he surfaces, but the water pulls him back under. The thirty-five pound youngster is on the verge of being swept away. He kicks and jumps frantically and finally makes it safely to the debris-covered embankment.

“Son, are you hurt?” his mother cries, nudging him up the bank to dry ground. As he shakes the water from his tawny brown coat, she says, “You have to stop wandering away.”

“I’m sorry, Mom. I just wanted to see what was down there.”

“Rivers are dangerous places for little elk,” his mother says.

A young elk stands dangerously close to the edge of a deep gorge cut by the roaring Lamar River in Yellowstone National Park.

Every spring as the snow melts, the rivers of Yellowstone rush over the barren landscape leaving huge crevices and ditches. Hundreds of elk graze in one area and consume the river-loving woody plants, especially the cottonwoods and willows, rarely allowing their tender shoots to grow tall. The elk’s sharp, point-ed hooves trample the roots which would have helped to anchor the soil and slow down seasonal runoff. The absence of one keystone species in the Yellowstone ecosystem contributes to this problem.

But that is all about to change. Missing for over seventy years, the elk’s primary predator has returned to teach little Wapi-ti and his herd how to run. The movement of the elk away from the rivers will allow the vegetation to grow, restoring the health of the riverbanks.

Renewed again, the timeless agree-ment between these two animals will help to sustain life in the valley.

11

Now, Let’s recap those clues.

The mystery animal:

1. Sounds like...Wind

howling through

the trees

2. Has golden eyes

3. Shares his food

with others

4. Keeps elk on the

move

“What was that?” screams Mochni.

“I don’t know,” exclaims Chinook.

Running For Home (excerpt)

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Exploring Prey & Predator Relationships

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Owl Pellet Essentials Dissection Lab

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Transcript of Owl Pellet Essentials Dissection Lab