An owl pellet typically takes a few hours to reach its final form after the owl has eaten, but it isn’t usually expelled immediately. Owls can store a pellet in a structure known as the proventriculus for as long as 20 hours before disgorging it. Since the stored pellet partially blocks the entrance to the digestive system, it must be ejected before the owl can eat again. Young owls do not produce pellets until they have begun to eat their prey whole.
The process of regurgitation lasts from seconds to several minutes. The pellet is forced out by spasms of the owl’s esophagus. These spasms can resemble painful coughing, but the owl is not harmed as the pellet remains soft and moist until it exits the body.
The shape and texture of a given owl pellet depends on the species owl and its prey. Pellets can be tightly compacted, oval, and furry, or loosely packed with an irregular shape. Pellets are moist when they are first ejected, but quickly dry out and start to decompose once they leave the owl’s body.