It's a fact of life that the moment a person wipes off a park bench or waxes the car a bird then promptly bombs the site again. No wonder some people consider birds unclean. But birds are among the tidiest creatures on Earth. What other animals put diapers on their young?
That's a bit of a stretch, of course. Only perching birds and woodpeckers package their waste. To be specific, their nestlings excrete gelatinous sacs while they defecate.
The term scientists prefer is "fecal sac," but no matter what it's called, the sac serves a function similar to that of the beloved diaper: it isolates waste so that a parent can then dispose of it. Often that involves flying some distance and dropping the sac into a river, lake, or swimming pool. An alternative (gulp) is for the parent simply to eat the sac.
Whatever fate the fecal sac meets, the advantages of its disposal are numerous. For starters, a clean nest is less likely to attract insects, parasites, and predators. Removing waste also helps keep the nest warm and dry. And for those adult birds that choose to ingest fecal sacs, these provide instant nutrition.
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