What do adult birds do with all the chick poop in their nests?

If you feed your chicks, then you will have to deal with chick sh*t, there’s no two ways about it, unless you want guano to accumulate in your nest. Here’s an adult emerging from its nest with a mouthful of faecal sac.

A faecal sac is a mucous membrane that surrounds the faeces of the chicks of some nesting birds. It allows the parents to more easily remove waste from the nest. A faecal sac is usually dispensed within seconds of feeding, presumably full of waste from the previous meal. Adults will wait in the nest after feeding their brood until a faecal sac is produced but they may have to prod the youngster’s cloaca with their beak to stimulate excretion.

Here’s the same parent a second or two later taking flight with a mouthful to discard the toxic waste away from the nest

Less toilet based photos of great spotted woodpeckers in an earlier post.