Would you notice if someone added their own child to your family, even if that baby looked just like your family members? Cuckoo birds have evolved to fool other birds into being foster parents by doing just that.

Cuckoos lay eggs closely resembling other birds' eggs in the nest of the hosts, then let the foster parents do all the hard work of caring for the eggs. After the cuckoo chick hatches, it shoves its nest mates out and dominates all the host parent's attention.


Just letting cuckoo home-wreckers waltz right in and kill your offspring wouldn't be too good for the survival of the fostering species. So, suspicious bird parents will toss different looking hatchlings out of the nest. But three species of the Australian bronze cuckoo have evolved to look like the host bird's offspring, according to researchers at the Australia National University's College of Medicine, Biology and Environment.

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Looking like a host family's chicks, allows cuckoos to fool the parents into accepting the cuckoos as the host birds' own.

The similarity lasts for about 8 days until the cuckoo's plumage starts to grow in, but at that point the host parents apparently are resigned to raising the cuckoo as if it were their own flesh and blood.

Each of the three cuckoo species has a particular host species they mimic and their chicks are colored either black, yellow, or pink to match.

IMAGE 1: Horsfield's bronze cuckoo; Wikimedia Commons

IMAGE 2: Cuckoos on left, respective host on right; COURTESY: N. Langmore