Savannah: These birds are cannibals, and they're neat! As in, tidy.

After their babies hatch, Black-headed gulls remove egg shells from their nest, and they do that to save their chicks from being eaten. Even though the shells are hard to spot, predators can still zero in on them fast. So the farther away they can get those shells, the safer their babies are. That means, weirdly enough, the safest parenting move is to leave the babies alone in the nest to go get rid of the shells.

In one experiment, eggs near shells were three times more likely to be taken by predators, so it really makes a difference. But they need to precisely time when they take out the trash. Some of their babies' predators are other Black-headed gulls, so having mom leave right when the chick hatches can mean death by cannibalism. But after the baby has fluffed up a bit, they're harder to eat, so priorities shift to the other predators' eye for shells.

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