Sibling negotiation

In Switzerland, the average size of a brood of Barn Owls is 5 owlets. These baby owls noisily discuss inside the nestbox while being raised for two months. Our research has shown that the owlets negotiate who will get the next prey brought in by their parents.

Hatching asynchrony

A particularity of Barn Owls is that they produce broods of nestlings who are not the same age. This happens because the female lays an egg every 2 or 3 days. She begins incubating as soon as she has laid the first egg and so the eggs hatch at intervals of a few days apart. This makes babies of different ages. In a brood of 5 owlets, the oldest will be, on average, 10 days older than the youngest. These age and strength differences could potentially lead to violent conflicts, especially around sharing food. And yet this is not the case!

Vocal negotiations

Our research into the communication between Barn Owl siblings has shown that the juveniles use their cries to negotiate who will get the next prey brought in by their parents. The young owls adapt their behavior with respect to the cries of their brothers and sisters and there are social rules to be respected, like allowing everyone a chance to speak. The principle is the following: longer or more frequent cries indicate stronger hunger. Each owlet expresses itself and it’s generally the one who is the hungriest who can request the prey directly from the parents, the others leave the way clear. In this way, there are no conflicts.

Altruistic behavior

These peaceful negotiations are accompanied by some other notable behavior. Mutual preening, which involves removing parasites and smoothing a sibling’s feathers, works as a kind of currency, and although there is stealing of food or even cannibalism of dead individuals, there are also gifts of food, especially when the latter is abundant. Older and healthier individuals are the ones who give their prey to the hungriest or to those who just offered preening before the meal. What this means is that Barn Owls, who are voracious predators and equipped with formidable weapons, reveal themselves to be mostly peaceful with their siblings.