They start their lives as horrifying fleshy demons with freakish mouths, but somehow, Gouldian Finches grow up to be beautiful birds prized for their gorgeous plumage. But back to those mouths for a moment, because as nightmare-inducing as they may be, they serve several functions.

One: the ornate patterns glow in the dark, helping their parents to locate their hungry babies and serve them a midnight snack. Two: they act as an evolutionary measure that helps parents distinguish their own young from imposter cuckoo chicks.

Unfortunately, cuckoo chicks have also started to evolve to have markings that mimic those of their target bird in what has been described as an “endless evolutionary arms race” - or, perhaps more accurately, a mouth race.