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 fecal sac (also spelled faecal sac) is a mucous layer, typically white or clear with a dark end, that encases the waste of certain nestling bird species. It enables parent birds to more easily remove waste from the nest. The young bird usually produces a fecal sac shortly after being fed; if not, an adult may prod around the youngster's cloaca to encourage excretion.