Ecosystems: Study of Owl
Pellets
Food Chains/Food Webs
What is an ecosystem?
Imagine yourself standing in the middle of a forest
observing everything around you.
You will see plants, animals, soil, sunlight, air,
water, minerals, and nutrients.
It is a living community which depends on each
member and its surrounding environment.
Every participant is important and if one becomes
more dominant than the others, the ecosystem can
develop problems.
What do ecologists do?
Ecologists are scientists that study complex
ecosystems.
They try to understand, from a scientific
point of view, what keeps everything living
and existing in a balanced and stable way
for very long periods of time.
Producers:
These are the living things which take the
non-living matter from the environment,
such as minerals and gases and uses them to
support life.
Green plants are considered producers and
are at the beginning of the food chain.
Consumers
These are living things that need the
producers to be their food.
Types of Consumers:
Herbivores- animals who eat only plants.
Carnivores- animals who eat other animals.
Omnivores- animals who eat both animals
and plants.
Decomposers- living things that feed off
dead plants and animals.
What is a population?
A population is a group of organisms of the
same species that live in a particular area.
The number of organisms in a population
change over time because of the following:
births, deaths, immigration, and emigration.
The increase in the number of organisms in
a population is referred to as population
growth.
Factors that limit population growth are
called limiting factors.
Factors that limit population
growth:
Food and water supplies-if there is not
enough, competition among the individuals
of the population would develop.
Light- those plants not getting enough light
will not grow strong and may even die.
Space- if there is not enough space, animals
compete for the limited space.
Predators- higher populations attract more,
when number of prey decreases, so does the
number of predators.
Diseases- can have an impact on birth rate
and growth rate.
Parasitism- relationship where one organism
feeds on the remains of another organism.
Predator:
They are animals that prey on other
animals.
The web of life in Nature is carefully
balanced and designed.
Each life-form on our planet is totally
dependent upon every other life-form, either
directly, or indirectly.
Owls:
They are predators.
They catch, kill, and eat other animals in
order to survive.
They seize their prey, usually a rodent or
other small mammal, and kill it with their
powerful feet. If the prey is small enough,
it is swallowed whole.
Owl Pellets:
The owl’s digestive system uses the nutritious
portions of the prey.
The undigested parts, such as hair, bones, claws,
teeth, etc. are regurgitated in the form of pellets.
These are found at roosting sites.
Usually 2 pellets at day are regurgitated. It takes
between 18 and 20 hours after a meal for the pellet
to come up.
The soft parts of the prey are dissolved by
enzymes.
The relatively weak stomach muscles of the bird
form the undigested fur, bones, feathers, etc. into
wet, slimy pellets. Even the most fragile bones
are usually preserved unbroken.
The pellets are produced and regurgitated, not
only by owls, but also by hawks, eagles, and other
raptors which swallow their prey whole or in large
pieces.
Predictions:
The number and species of mammals found
in the pellets.
The origin of the pellets.
The characteristics of the ecosystem in
which the pellet-maker fed.
Pellet Dissection:
Place the pellet on a sheet of white paper.
Using gloves and forceps, separate the bones of
the animals from the fur and/or feathers.
Clean the bones of debris and sort them according
to type.
Using the charts and keys identify prey mammals.
Record the kinds and numbers of prey you find in
your pellet on your data sheet.
Discuss the class record.
Results:
Use class data to prepare a graph of animals
found in owl pellets.
Sort bones and lay out bones of a skeleton
on a flat sheet of paper. Glue bones of an
animal together to form a skeleton.
Make a collections of drawings or
specimens of organisms in undissected owl
pellets.
Collecting Owl Pellets:
Can be collected in old barns.
Hundreds of pellets can sometimes be found on
the floor beneath the roost of a family of barn
owls.
Barn owls are most common in areas of open
meadows and fields where large numbers of small
mammals are active at night.
Pellets that have been collected should be dried
and stored in a closed container and fumigated to
prevent the growth of fur-eating insects.