Transcript OwlPelletDissection

Owl Pellet Dissection
Owls of Maryland
•
1.
2.
3.
4.
5.
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
• Owls have special
adaptations that enable
them to hunt at night.
1. Their eyes are large and
fixed, with binocular vision
and good depth
perception.
2. 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.
3. Their eyes are also
extremely light sensitive,
allowing them to see well
at night.
Adaptations as
predators
Barred Owl
Owls as predators
4. Owls rely on silent flight
to surprise their prey.
5. The shape of the owl’s
flight feathers muffles
the sound wind makes
as it flows past them.
6. 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
An idealized food pyramid
• 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
• 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.
• 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
Owl Pellets
Species diversity
has two components:
1. Species richness: how many different
species are present in a habitat
2. Relative abundance: total number of
individuals of each species present given
in % of total.
Species diversity has two
components:
1. Red Maple
2003
33%
2. Black Gum
18%
3. Sweet Gum
17%
4. Oaks
14%
5. American Holly
8%
6. Loblolly Pine
6%
7. American Beech
4%
1. Species richness:
how many different
species are present
in a habitat
2. Relative abundance:
total number of
individuals of each
species present
given in %
Common Genus
Name
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
Type and
Vole
# of bones
Skulls
Jaws
Shoulder
blade
Front legs
Hips
Hind legs
Assorted
ribs
Assorted
vertebrae
# of
animals
Shrew
Mole
Rat
Mice
Bird