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Evolution: Nature's loudest love cry

Single-flap koting gas (Procnias albus) are quite noticeable in the rainforest of northern Brazil: They have pure white plumage, a long flap of skin hangs from their beak - and they woo females so deafeningly that biologists wonder how they can stay near the calling males without hearing damage to suffer. As measured by Jeffrey Podos from the University of Massachusetts at St. Amherst and Mario Cohn-Haft from the Instituto Nacional de Pesquisas da Amazônia in Manaus, the bird's courtship cry is the loudest among birds and perhaps even in the animal kingdom as a whole. They published their study in "Current Biology".

Some of the love screams reach up to 125 decibels, according to the measurements: This corresponds roughly to the noise of a fighter plane flying low and is above the threshold value at which hearing damage occurs in the human ear even with short-term exposure. And the volume is well above the calls of the - nomen est omen - Schreikotingas (Lipaugus vociferans), which was previously considered the loudest bird.

The two scientists were astonished that such small birds can make such a noise: The animals weigh only 250 grams, but their vocal organs clearly outperform that of howler monkeys and bison. Both mammals are also known for making conspicuous vocalizations. Podos and Cohn-Haft were even more fascinated by the fact that females voluntarily expose themselves to this at close range. “We often observed females perching on the same branch as calling males. And exactly then they uttered their loudest scream and turned the hardest - as if they wanted to punch the final chord directly at the females, ”says Podos, describing the behavior.

A few anatomical adjustments may help the single-flap koting gas. They have unusually thick and particularly well developed abdominal muscles and ribs. However, the volume is at the expense of the ringing length; this decreases as the number of decibels increases, probably because the birds then simply run out of air. Future studies should find out more about the behavior of the little-researched birds - and why the females do not suffer any obvious damage even in the immediate vicinity.