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The Kid Should See This

Why aren’t bird nests covered in poop?

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“Earlier this year I noticed a bird nest with a single bright blue egg sitting on my front porch,” explains video producer Estelle Caswell in the video above, one in a series of Vox videos created for kids.

Over the course of a few days, the single egg turned into four, and in a few more days, they hatched. What I witnessed over the course of watching these birds grow was magical, but it also left me with a lot of questions about what goes on in the beginning of a bird’s life.

My biggest question: Where does all the bird poop go?

Ecologist and ornithologist Dr. Michael Murphy answers that question—it’s a pretty surprising answer—and explains why robin eggs are blue, what the babies eat, when the babies can finally fly, and more.

robin eggs
baby birds eating worms
More about bird poop and clean nests from Murphy and ecologist Juan Diego Ibáñez-Álamo at

A fecal sac is essentially a diaper… It provides the parents with a very self-contained structure that allows them to easily pick up feces and remove them from the nest. It’s a way of getting rid of all this material that might otherwise smell and decompose…”

Some birds have evolved a more efficient method of dealing with fecal sacs: They swallow them.

Why? The best guess—the one with the most research—is that birds eat fecal sacs because nestling poop serves as a nutritional treat (a trait known as coprophagia). “Parents will eat the feces because the nestlings cannot completely digest the food that they eat,” Ibáñez-Álamo says. “There is still energy and nutrients available in those sacs.”

Related resources include the Audubon’s Birding site and The Cornell Lab of Ornithology’s K-12 Education site.

TKSST is full of nest and poop-related videos, including:
• Life inside a Purple Martin nest
• How do hummingbirds build their tiny nests?
• Up close with a Carolina Wren feeding its nesting babies
• How do cliff swallows build their mud pellet nests?

Bonus: Can bird poop make clouds?

And previously from Vox for kids: The Secret History of Dirt.

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