Some bird species eat the fecal sacs of their nestlings, which are similar to bird diapers. Scientists have proposed several reasons why parent birds eat fecal sacs, including: Energy restoration: Fecal sacs may help restore energy lost during incubation. Nutrients: Nestlings can't completely digest their food, so the sacs may still contain nutrients and energy. Age: Some birds eat the sacs throughout the nesting period, but others only eat them when the chicks are young. As the chicks get older, their digestive tracts become more efficient, leaving less usable material in their feces
