Baby Bird Poops into Fecal Sacs Which are Equivalent of Disposable Diapers

These Robin baby birds were lying in their nest as mother robin was feeding them. One of them pooped into a fecal sac, which is a sort of a bag made of mucous membrane so that their mom can remove it easily from the nest. The fecal sacs are a common feature of baby robins and are a human equivalent of disposable diapers.