What’s that in my nest? How the evolutionary arms race between cuckoos and hosts creates new species

A superb fairy wren foster parent about to feed a Horsfield's bronze cuckoo chick. Mark Lethlean

How do new species arise? And why are there so many of them? One possible reason is the arms race between animals such as predators and parasites, and the victims they exploit.

Many predators and parasites have evolved specialised strategies to avoid detection, such as mimicking their prey or host. In these cases, when the exploiter adopts a new victim, it needs to mimic the new victim to succeed.