You might hire a nanny to take care of your kids while your out, but did you know that some animals do too?

An Australian bird, called the superb fairy wren, rely on other birds to help raise their young. This strange animal behavior is called cooperative breeding, and is actually more for the moms than the chicks.

The mother fairy wren knows that her chicks will be looked after and fed by a flock of nannies, so she invests less energy in her eggs. Cooperatively-bred eggs are typically smaller and contain less protein than other eggs. Therefore, by literally putting less into her eggs, the mother fairy wren conserves energy, lives longer, and is able to produce more eggs.

In this way, fairy wrens use cooperative breeding as an evolutionary strategy to perpetuate the species.