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Owl Pellets

Background

Owl pellets are masses of bone, teeth, hair, feathers and exoskeletons of various animals devoured by raptors, or birds of prey.  Pellets are produced and regurgitated not only by owls, but by hawks, eagles and other raptors that swallow their prey whole of in small pieces.  Owls feed  early in the evening and regurgitate a single pellet approximately 20 hours after eating.  Unlike snakes, the protein enzymes and strong acids which 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 wet slimy pellets.  In this process even the most fragile bones are usually preserved unbroken. The owl pellets that you will be examining in this lab have been collected and  fumigated from common barn owls.  Owl pellets themselves are ecosystems, providing food and shelter for communities which may include clothes moths, carpet beetles and fungi.  Clothes moth larvae are frequently abundant in pellets, feeding on fur and feathers.  The black spheres about the size of periods (.) that are found in the pellets are the droppings of the caterpillars.  The larvae metamorphose near the surface of a pellet in cocoons made of fur.    Some owl that may be found in Georgia the Barn Owl, Common (Tyto alba) ,Barred Owl (Strix varia)   Great Horned Owl (Bubo virginianus) and Eastern  Screech Owl, (Otus asio) .

Materials

Owl pelletsGlueDissecting NeedlePaper

Procedures

1.

Unwrap your owl pellet.  Measure the approximate length and width of your owl pellet in cm

2.Weight your owl pellet in grams to the nearest tenth (one place after the decimal point)

3.Make observations about the surface of your owl pellet

4.Carefully tease apart your owl pellet, being careful not to break or lose any small bones. 5.Choose a skeleton and use the attached identification sheets to reconstruct the skeleton of the prey.

6.After obtaining all of your data, dispose of the fur and feathers from your pellet and place any bones in a labeled petri dish.

Data and Observations

1.      Length of your owl pellet_______        Average class length_______

Width of your owl pellet_______         Average class width_______

Mass of your owl pellet_______          Average class mass_______

2.      Total number of prey animals found_______

Birds_______Rodents_______

Insects_______Other_______

Average number of prey per pellet_______

3.

Use one of the skeletal illustrations provided in class to reconstruct a half skeleton from the remains found in your owl pellet.  Each group may turn in one skeleton reconstruction with each member’s name on it.

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