When a bird of prey eats its prey and then regurgitates the bones and fur or feathers, what is that regurgitation called? There are at least two names for this regurgitation. Pellets in raptors are often colored brown to gray or black depending upon their freshness and contents.
The action of pellet casting is kind of bizarre to observe, and not for the faint of heart. The bird goes through a minute or so of chest and neck stretches resembling upper body yoga moves, then it finally elongates and arcs its throat downward, and drops the pellet from its beak. Some birds might shake their bills side to side to dispatch the pellet.
Pellets can be found anywhere that a raptor perches, often a roosting or nesting site. If you are concerned about exactly what you might be picking up, watch especially for bits of bone and tiny skulls to discern an owl pellet. Most biology teachers know that pellet dissections can be exciting and tactile introductions to the scientific study of birds. The pellet was an intricate mass of pure interlocked beetle parts.
If these birds couldn't produce or regurgitate pellets, their food would get backed up and they would essentially die. Most teachers, students and hobbyists who dissect bird pellets use the ones produced by owls. Typically, they produce the largest pellets filled with a wide range of animal parts from their prey.
Dissecting a pellet from an owl can yield rodent exoskeletons, insect shells, bills, beaks, claws, hair and fur. Out of all the pellet-producing birds, owls are the most easily accessible, therefore making their pellets more common than others. Owls love the dark shade of farms, silos, outdoor storage buildings, sheds, and large coniferous trees. Oftentimes, people living with any of these structures can walk out there on any given day to find a slew of owl pellets owls produce pellets daily.
While their exact numbers are unknown, there are believed to be around to different species of hawks worldwide. Although, in North America, there is only about 25 different species. Quite a few others do as well, including hawks. However, owl pellets tend to be larger than those ejected by hawks because owls tend to gobble prey whole, while hawks rip off small pieces of meat.
Once formed, an owl pellet moves from the gizzard back into the proventriculus, where it may remain for as long as 10 to 20 hours. Its presence prevents the owl from swallowing fresh prey, so the bird often regurgitates, or casts , the pellet shortly before commencing hunting again.
The owl often casts the pellet from a favorite roost or depending on the season a nest. The entire process of hacking it up can take upwards of a few minutes. Owls usually cast one to two pellets per day.
Generally speaking, and not surprisingly, smaller owls tend to produce smaller pellets and larger owls produce larger pellets. The pellets of a northern saw-whet owl, for example, which is one of the littlest North American owls, tend to be less than an inch long. Large species such as great horned, great gray and snowy owls may cast pellets several inches in length, by contrast. The same goes for shape, though pellets, generally speaking, are roughly cylindrical.
Freshly cast owl pellets are moist, but they quickly dry out, and they tend to be virtually odorless. Owl pellet dissection — which should only be undertaken with sterilized pellets due to the risk of contracting bacteria or viruses — reveals what a given owl has been chowing down on.
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