If you thought that humans were the only creatures that created prisons or cages for other beings, think again. Falcons in Morocco’s Essaouira archipelago have recently been observed imprisoning other birds and detaining them for several days to keep them fresh for a later meal, reports New Scientist.

It sounds devilish, like some sort of avian inquisition. And for the birds being held as prisoners, it's probably their worst nightmare. For the falcons, however, it just makes good sense. When you can't refrigerate your prey, hold them alive as prisoners instead.

This behavior has only been observed in Eleonora’s falcons, specifically those that nest on the barren Moroccan island of Mogador. Their methods of imprisoning their prey can range from crude to surprisingly sophisticated. For instance, some small birds were simply jammed into rock crevasses in ways that made escape impossible. Others were dropped into deep holes or fissures and had their flight and tail feathers stripped off, to make them incapable of flying to their freedom. The falcons would then return to their prey days later to consume them or feed them fresh to their young.

The behavior is only usually observed seasonally, in late summer when the falcons lay their eggs and rear their chicks — a timing that helps to explain how and why the odd conduct may have developed. This is also around the same time that many smaller birds are in the middle of their annual migration across the region. The influx of potential prey is a boon for the falcons as they anticipate more mouths to feed, but that prey can also be fleeting. By imprisoning live birds, the falcons can store them to feed to their hungry chicks as needed.

Most of the rest of the year, Eleonora’s falcons actually prefer eating insects. So their bird prisons are only a part time thing.

It's sophisticated behavior nonetheless, if not a bit sinister. The Moroccan colony is also the only population of falcons this behavior has been observed in so far, making them unique, not only among their own kind, but also among birds in general.