The Bird That Impales Its Prey
In one of our recent mental_floss videos, Emily Graslie introduced us to the shrikes, a family of birds with a nasty habit of impaling their prey on thorns and barbed wire fences.
The birds’ feeding habits are hard to ignore, and common names for the birds around the world reflect the grisliness and perceived cruelty of them. In English-speaking countries, they’re known as butcherbirds. In East Africa, a shrike is called “jacky hangman.” The Dutch call them canary biters. The Germans have two great names for them—Neuntoter (“nine dead”) and Raubwurger (rauben, “to steal” + wurger, “strangler”).
Why do shrikes go all Vlad the Impaler on their prey? Over the years, biologists have offered several explanations.
Shrikes lack the impressive talons of many other carnivorous birds, like eagles and owls, and instead rely solely on their beaks to kill and dismember prey. Impalement holds the prey in place and allows the shrikes to pull their meal apart and eat it, acting like the “fork” to their beaks’ “knives.”
Impaled prey acts like a pantry for the birds, too, and they can return to a large impaled animal for several feedings, store food when prey animals are less active, or share the kills with their mates and offspring. A large cache of impaled critters might also advertise a shrike’s quality as a mate, and males with bigger larders have been shown to mate earlier and have more kids.
Letting prey hang out for a while could also let the shrikes feed on animals that other predators can’t exploit and don’t compete for. At least one species, the Loggerhead Shrike, regularly feeds on monarch butterflies and lubber grasshoppers—both of which have chemical defenses that make them unpalatable and even dangerous to other birds. The shrikes don’t eat these insects “fresh,” though, but only after letting them sit on a spike for a few days and allowing the toxins to degrade to the point where the insect is safe to eat.