What exactly is a parasite? Well, parasites are animals that live off of other living animals. Brood parasites, though, place their eggs in other animals’ nests. But why do birds parasitise? In my opinion it’s because they’re the lazy, good-for-nothing parents of the bird world. The real reason is that it lessens the chance their eggs will be destroyed. If you put an egg in someone else’s nest, the dangers that would threaten an egg usually wouldn’t be a big threat anymore. Except for fairy-wrens.
In the dense Australian forest, a small, bright bird flits among the plants searching for some nesting materials. This fairy-wren is almost ready to build a nest. Most birds would look at their nest and not notice an unusual egg. Not fairy-wrens. They have developed a trick through the course of evolution. You can’t see in the dark, domed nest of fairy-wrens, but when the chicks are in the egg, the mother fairy wren will cheep a code which only the baby wrens can know what to do with. So when the chicks hatch, the mom listens for the code in their begging call and can single out the cuckoo chick as an imposter.
Some other species aren’t so lucky. Take the reed warbler for an example, these little birds build their nests in the tall reeds of Europe. The common cuckoo is a major brood parasite of the little birds. Ever seen a dog with a ball that seems way too big for its mouth? Imagine the same thing with a chick and a reed warbler nest. The common cuckoo uses the push-from-a-height technique which involves that little parasite using its back to push the eggs over the rim of the nest.
But wait! There is another brood parasite that uses quite a different technique. The greater honeyguide of Africa has quite a history, from leading natives to honey to being a brood parasite, these little birds are remarkable. About the different technique, honeyguides bite their nestmates and then flashes yellow markings imitating more hungry mouths.