Brood parasite

So, you know how birds make nests to lay their eggs and raise their babies, right? Well, sometimes there are birds who don't want to make their own nests and take care of their own babies. Instead, they sneak into another bird's nest, lay their eggs in there, and let that bird take care of the eggs and the babies that hatch from them. This is called being a "brood parasite".

It's kind of like when you go to a friend's house for dinner and eat all of their food without bringing any food of your own. You're being a "dinner parasite"! But that's not a nice thing to do, and being a brood parasite isn't nice for the other bird either. The bird that got tricked into taking care of the other bird's eggs and babies might not have enough resources to take care of all of them, or their own babies might not get enough attention or food.

Some birds that are really good at being brood parasites are called cuckoos. They are really sneaky and lay eggs that look just like the eggs of the bird they are tricking, so the other bird doesn't even realize that they're sitting on someone else's eggs. But some birds are really good at figuring out when they have a brood parasite in their nest and they will either abandon the nest and start all over again somewhere else or simply remove the foreign egg from the nest.