Amazonian Bird Mimics Poisonous Caterpillar

A young cinereous mourner (Laniocera hypopyrra), which looks completely different from the dull gray adult. Santiago David

If you're a bird, especially a nestling too young to leave home, being eaten is a real possibility. In fact, predation is the leading cause of "nest failure" for birds, which is exactly what it sounds like.

So what do you do if you're avian and happen to live in the Peruvian Amazon, with many animals, like snakes, that are looking for nests to raid? One bird species known as the cinereous mourner (Laniocera hypopyrra) has come up with a nifty solution, according to a new hypothesis: its young look and even move like a type of poisonous caterpillar, which carnivores have learned to avoid.

According to a study published last month in The American Naturalist, the resemblance between these chicks and caterpillars may not be merely a coincidence. The authors argue it's a case of Batesian mimicry, in which a harmless (and likely tasty) organism mimics one that's toxic. This tactic is found throughout the animal kingdom, but is rather rare in large animals; one good example is the viceroy butterfly, which looks similar to poisonous monarch, but is itself not full of toxins.

A caterpillar in the genus Megalopyge, which is so toxic that it has proved fatal to humans in rare circumstances. A new study suggests bird chicks are mimicking these caterpillars. Wendy Valencia

Upon hatching, the cinereous chick is covered with distinctive feathers that are bright orange with white barb-like tips, and six days later it starts to "move its head very slowly from side to side (in a 'caterpillar' movement) when disturbed," the scientists write in the study. "These traits give it a resemblance to a hairy, aposematic [or poisonous] caterpillar."

The scientists think the chicks are mimicking a caterpillar in the genus Megalopyge, which is so toxic that it has proved fatal to humans in rare circumstances. Similar critters have been described by others as looking like a living version of "Donald Trump's hair."

The larval form of a flannel moth, known as a puss caterpillar, that is related to the poisonous species that cinereous mourner chicks mimic. Phil Torres /

The chicks' shockingly orange appearance is all the more striking since adult cinereous mourners are a dialed-back dull gray. The researchers argue that their Batesian mimicry theory is more plausible than a 1982 hypothesis that the chicks adopt this appearance to resemble "moss-covered fruit," since it was based on a limited number of bird specimens and moss isn't usually orange and white.

A side-by-side view of the chick (e) and caterpillar (f), in case you couldn’t tell them apart. The American Naturalist / Santiago David and Wendy Valencia