The blue-throated warbler teaches its chicks a password in case of hand tricks

The world is full of all kinds of strollers. You should keep passwords to yourself.

This is also understood by the Australian blue-throated warbler. A small sparrow bird requires strong identification even from its own chicks. When the cuckoo arrives to attempt identity theft, its plot is immediately revealed.

Blue cucumbers ( Malurus cyaneus ) live in southeastern Australia and Tasmania. The dog gets a handsome blue plumage during the ringing season. Maluri lay 3–4 eggs at a time and incubate them for two weeks.

The peace of the nest is stalked by the whistling voro, the Australian bronze cuckoo. Like other cuckoos, it tries to float its own egg into the nest of the malur. When the chick of the hand hatches, it pushes the maluri’s eggs into the hill and remains a dishonest livelihood for the unsuspecting mother.

Not only that the maluriemo also foreshadows evil. When it incubates its eggs, it sings to them a song with a secret melody hidden in it. It teaches the same tune to its wing – so the couple develops its own secret language.

Even though the malur chicks are still in the egg hatching, they can hear the note and learn it when exposed to it enough. Likewise, a human child hears the sounds of the outside world already in the womb, and recognizes its mother’s voice when it is born.

When the malur’s chicks then hatch, the condition of sustenance is knowing the password. The cubs coo to a familiar tune, and the mother recognizes hers.

The cub that took over the nest can’t sing, so it has to starve. It doesn’t have time to learn the tune, because the Maluri only starts humming at the end of incubation. The cuckoo hatches when the song has only been heard for a couple of days.

Malur’s own chicks hatch clearly more slowly. They get to study notes in the egg for almost a week.

Ecology Diane Colombrelli-Négrel came up with a cunning defense in what he did 15 years ago in the studypublished by Current Biology. The trick works so well that almost half of all maluri couples avoid raising foreign schemers.

People in the same club can have a secret handshake. So was this a secret handshake?