Owl pellets, or regurgitation, are materials from the bird’s prey


You may have been following recent news about the City Nature Challenge in which Rio Grande Valley folks uploaded nature photographs to iNaturalist.org’s website database in order to document the diversity of the Valley’s habitat.

Photographs that were considered signs-of-life and were accepted included feathers, roadkill, scat and animal and bird tracks. One peculiar find that shows something left behind by a critter is known as an owl pellet.

Owl pellets are composed of indigestible materials from the bird’s prey, including feathers, teeth, fur and some bones along with the owl’s digestive fluids.

The pellets are not scat, as they have not passed through the owl’s digestive system, but have been regurgitated because they can’t be digested.

Owl intestines have weak digestive enzymes and cannot break down hard-to-digest materials. While digestible materials pass through, the rest is held in the owl’s gizzard. When full, an owl will stretch its neck up and forward, open its beak and eject the pellet without retching.

Owl pellets usually measure one-and-a-half to three-and-a-half inches long. When regurgitated, it is roughly the same shape as a particular owl’s gizzard and can be spherical, oblong or plug-shaped.

Most adult owls will produce two pellets a day. The pellets can easily be found underneath their favorite roosts.

Barn owl pellets are easily recognized because barn owls’ diets consist primarily of rodents; therefore, those pellets are generally uniform in color, black when fresh, with obvious bits of other matter. The pellets gradually turn grey as they age. Owls also eat other birds, doves, pigeons and small songbirds. Some species of owls have diets that include fish, carrion or insects.

Such pellets are common to all birds of prey that swallow their food whole, including hawks and eagles. In falconry, it is called a casting. Other species that produce pellets include grebes, herons, cormorants, gulls, terns, kingfishers, crows, jays, swallows and most shorebirds.

Owl pellets have no smell. This is not the case with Turkey Vultures, who have the same ability of regurgitating undigested food. Some avian do this spontaneous regurgitation as a defense when startled or harassed. The extremely putrid-smelling vulture regurgitation can be ejected up to 10 feet and can burn its harasser since it is highly acidic. Herons, gulls, terns and kestrels also rely on this type of defense.

Although owl pellets can be a fascinating find and interesting to pull apart to see what a bird’s diet was, it’s extremely wise to take caution before handling one. Wearing medical gloves, wrap each pellet in aluminum foil and place it in a 325 degree Fahrenheit oven for 40 minutes. This treatment should kill bacteria such as E. coli and other harmful things that might be present.

Anita Westervlet is a member Rio Grande Valley Chapter, Texas Master Naturalist and provides monthly stories to The Monitor.