By Pratik Pawar
If ever there were a competition to rank sibling relationships in the animal kingdom, barn owls would be close to the top. That’s because elder barn owlets will sometimes give away their meal to their younger siblings. Such cooperative behavior has been reported in adult nonhuman primates and birds, but rarely among young (SN: 2/6/12).
“I don’t know any other species where you can find it,” says Pauline Ducouret, an evolutionary biologist at the University of Lausanne in Switzerland. But scientists weren’t sure what prompted the food sharing. Now, observations of nests show that elder barn owlets offer their food to their younger siblings in exchange for grooming, Ducouret and her colleagues report in the July issue of the American Naturalist.
Barn owls (Tyto alba) raise six chicks at once, on average, and sometimes as many as nine (SN: 9/19/17). But not all chicks hatch at the same time, which means that elder chicks are usually healthier and larger than their younger brothers and sisters.
That’s because all chicks are entirely dependent on the parents for food, and food, in this case, is usually a small rodent, like a vole or a shrew, that can’t be easily split. So at any given visit, mom or dad can feed only one chick at a time. In many bird species, the eldest siblings would simply outcompete the rest, but not barn owls.