A fecal sac (also spelled faecal sac) is a mucous membrane, generally white or clear with a dark end, that surrounds the feces of some species of nestling birds. It allows parent birds to more easily remove fecal material from the nest. The nestling usually produces a fecal sac within seconds of being fed; if not, a waiting adult may prod around the youngster's cloaca to stimulate excretion.
A mucous membrane that encases the waste of some nestling birds is called a fecal sac (also spelled faecal sac). This structure helps parent birds remove waste from the nest. Young birds usually produce a fecal sac shortly after being fed; if not, an adult may prod around the youngster's cloaca to stimulate excretion.