It turns out falcons in Morocco could be the ultimate bad guys. On the Essaouira archipelago, researchers witnessed a species of bird called the Eleonora’s falcon capturing smaller birds and holding them captive for days before killing them.

In Alauda, a French ornithology journal, Abdeljebbar Qninba of Mohammed V University reported the predatory behavior he and his team witnessed while conducting a census of falcons on Mogador, one of the archipelago’s islands, in 2014. Today the island is a nature preserve, but it also hosts the ruins of an abandoned fortress and prison. There may still be prisoners on Mogador – but they have wings.

falcon-2Image: Conselleria de Medi Ambient i Mobilitat

For most of the year, the falcon’s diet consists mainly of insects. But when they lay their eggs in late summer, the falcons begin catching other birds to feed their growing families. Stocking up on food ahead of time presents a problem, though, as the meat may dry out or begin to rot before the chicks are hatched. The falcons have come up with a solution: they catch smaller migratory birds like the common whitethroat and the tree pipit alive, and then trap them until dinnertime.

Researchers found birds wedged tightly in rock fissures near the falcons’ nests. In some cases it appeared the falcons had removed the smaller birds’ tail and wing feathers, rendering them unable to fly away.

Some experts are skeptical of the researchers’ findings. Rob Simmons, an ornithologist at the University of Cape Town in South Africa, told New Scientist he’s not sure the Eleonora’s falcon is smart enough to imprison prey for later. Raptors like the falcon often begin plucking prey before killing, so the injured birds may have been escapees.

“I don’t believe a falcon has the cognitive ability to ‘store’ prey like this,” Simmons said. “I think the birds’ prey may simply be escaping and finding refuge.”

falcon-1Image: Jürgen Dietrich

Journal reference: Alauda, vol 83, p 149