Some animals are either unwilling to work or just very inactive. Surprisingly, they're just as successful as hard-working animals.

Cuckoos don't build a nest and don't raise their own young. Instead they lay their eggs in the nests of other birds and leave the host bird to hatch the unwanted extra egg and feed the chicks.

For two months of the harsh Antarctic winter thousands of Emperor Penguins huddle together, eating nothing and going nowhere. Why? As there is no material for nest building, they must carry their single egg on their feet and keep it warm under a fold of skin until it is ready to hatch.