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About Owl Pellets

owl pellets

Both hawks and owls consume quantities of bone, feathers, and fur when eating prey.  After the bird has digested it’s meal this inert indigestible material  is rolled and compacted in part of the raptor’s digestive tract known as the gizzard, to form what is called a pellet or casting.  This is regurgitated several hours after feeding or before the next meal.  It isn’t known how many pellets a wild raptor produces per day so that accurate figures on daily intakes are unavailable.  However, they do yield information as to the type of prey consumed.   By comparing bones, feathers, and fur with the same material in an identified collection, identification of the dissected items is fairly easy.  In many cases if a large enough sample of pellets is examined it is possible to obtain a fairly accurate record of the diet of one raptor or the diet of a species.  It is also an indication of population densities and vulnerability of the prey species identified, since prey is taken in proportion to it’s relative density.

Accuracy in making counts of prey items depends on the type of pellet that is being worked with.  Because of differences in feeding habits and physiology, hawks and owls produce pellets that differ in their ability to be examined quantitatively.  Owls tend to swallow small prey whole and larger prey in several pieces.  They don’t take the time to pluck their prey.  Also their digestive tract does little or no damage to the bone consumed.  This results in pellets that usually contain whole skeletons that are relatively undamaged.  Hawks on the other hand, pluck their prey before eating and then tear it into small pieces before swallowing, consuming varying amounts of fur and feathers.  They also digest bones more completely than owls so that their pellets often contain little osseous remains.  Identification of prey species must be made by pairing incisors which are usually present.  Fairly accurate counts can be made in this manner by someone trained in their identification .

It can be expected that the number of individual prey items found in owl pellets closely represents the actual number of animals consumed.   Other factors such as the number and size of species represented and the durability of the pellet help in making accurate counts of prey items.