Nature & Environment

This Bird from the Amazon Rainforest Looks Like a Caterpillar to Avoid Being Eaten by Predators

Catherine Griffin
First Posted: Feb 25, 2015 12:15 PM EST

Birds are usually known for eating caterpillars-not looking like them. But a new study reveals that at least one bird actually mimics the appearance of a poisonous species of caterpillar in order to avoid being eaten by predators.

In tropical habitats, nestlings have to cope with high rates of predation. That's why birds have developed nesting strategies to allow them to escape predators that range from other birds to mammals to snakes. In this case, though, nestlings do something unusual: they look like an insect.

While working on a long-term avian ecological study, researchers discovered something interesting. They found the second nest ever described for the cinereous mourner, a type of bird. When the chicks hatched from the nest, they had downy feathers with long orange barbs with white tips; it was so unusual, that the researchers couldn't help but investigate further.

The researchers noticed that the nestlings moved their heads very slowly from side to side in a way that's typical of many hairy caterpillars. While working in the area, the investigators also found a poisonous caterpillar that was a similar size and had similar hair coloration. This made the researchers realize that it was likely that the birds intentionally mimic the caterpillar in order to avoid predation.

The findings reveal a bit more about what kinds of remarkable adaptations these birds have evolved over time. It's likely that the coloration decreases the rate of nestling mortality, and may increase nesting success in the species.

The findings are published in the journal The American Naturalist.

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