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Lab Manual
Natural History Event Species List



1. To obtain experience in natural history techniques.
2. To identify the
prey found within owl pellets.
3. To better understand the kind of information that can be obtained from owl pellets.


From the deer pounced upon by the mountain lion to the ant snapped up on the tongue of a horned lizard, predator-prey relationships command our attention. Witnessing the actual event of predation is rare; therefore, scientists studying predator-prey relationships often must resort to examining the aftermath (carcasses, feces, and pellets). Owls are a major nocturnal predator, especially on small mammal populations. Owls tend to swallow their prey whole. The "mouse" slides down the esophagus and into the stomach (proventriculus in birds) where acids begin to breakdown the meat. The fur and bones are undigestible. The "mouse" goes to the muscular gizzard for mushing to expose new surfaces to the stomachs acids. Finally, all the meat has been dissolved and passed into the long, tortuous passageways of the intestines for absorption and use by the owl. The remaining fur and bones are packed into a neat pellet and regurgitated. This is a nice way to reduce weight for flight. Other birds that take in a lot of indigestible parts (fur, feathers, scales, bones, insects shells,etc.) in their diet also regurgitate pellets (e.g. other birds of prey, fish-eating birds, beetle-eating birds, etc.). Therefore, by identifying the pellet parts, one may study the diet of the bird on a day-by-day basis. It is much easier to collect the pellets below the bird's roost than to chase the bird around waiting to see what it eats. We will study the pellets from the Common Barn Owl (Tyto alba) (14-20" in height) that occurs throughout most of the U.S. including Tucson.


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