Owl Pellet Dissection

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Owl Pellet Dissection
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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

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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.

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Owls as predators

• Owls rely on silent flight to surprise their
  prey.
• The shape of the owls 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.

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The Food Web
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Owl Pellets

• 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).
• Depending upon the prey eaten, 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. In this process even the most fragile
  bones are usually preserved unbroken.

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• The owl pellets that you will be examining in
  this lab have been collected and fumigated from
  common barred owls.
• Owl pellets themselves are ecosystems, providing
  food and shelter for communities that may include
  clothes 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.

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Owl Pellets

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

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Estimating Species Diversity

• Species richness the total number of different
  species
• Species abundance the abundance () of each
  species

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Worksheet
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Prey Analysis Data chart