1. Owl Pellet Dissection

2. Owls of Maryland
Five species of owls live in or pass through Maryland.
Barn owls
Great Horned owl
Barred owls
Eastern Screech owl
Northern Saw-whet owl
Barred Owl

3. Adaptations as predators
Owls have special adaptations that enable them to hunt at night.
Their eyes are large and fixed, with binocular vision and good depth perception.
Because owls are unable to move their eyes, they 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

4. 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.
These are all perfect adaptations for finding and catching prey at night, and explain why owls have become the most efficient “hunters of the night”.
Saw-Whet Owl

5. An idealized food pyramid
Figure An idealized pyramid of net productivity. In the case illustrated here, 10% of the energy available at each trophic level is converted into new biomass in the trophic level above it. Notice that primary producers convert only about 1% of the energy in the sunlight available to them into primary productivity. In actual ecosystems the decline in productivity with the transfer of energy between trophic levels varies with the particular species present; a 10% transfer of energy (ecological efficiency) is a rough average.

6. 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.
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. This type of material has little nutritional value and must be passed from the body.
Owl Pellets

7. The owl pellets that you will be examining in this lab have been collected and fumigated from common barn owls (Tyto alba).
Owl pellets themselves are ecosystems, providing food and shelter for communities that may include moths, carpet beetles and fungi.
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.

8. Owl Pellets
Ecologist examine owl pellets to estimate the diversity of prey species
The contents are a direct indicator on
What the owl has fed upon.
Species richness
Species abundance
Important information for species management and protection

9. Species diversity has two components:
Species richness: how many different species are present in a habitat
Relative abundance: total number of individuals of each species present given in % of total.

10. Species diversity has two components:
Species richness: how many different species are present in a habitat
Relative abundance: total number of individuals of each species present given in %
2003
1. Red Maple
33%
2. Black Gum
18%
3. Sweet Gum
17%
4. Oaks
14%
5. American Holly 8%
6. Loblolly Pine 6%
7. American Beech 4%

11. Common Name
Genus
Freq Found
Vole
Microtus
70%
Shrew
Sorex
20%
Mole
Scapanus 5%
Deer Mouse
Peromyscus 2%
House mouse
Mus
Rat
Rattus 1%
(small bird)
Hirundo
rare

12. 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