Ecosystems: Study of Owl Pellets

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.

Ecosystems: Study of Owl Pellets