Earthworms have tiny bristles called setae which usually stay inside of their bodies. They can, however, jab them into the surrounding dirt to help them move forward. What is another way that earthworms often use their setae?

to anchor themselves to the ground when a bird tries to pull them away

Explanation:

Earthworms or worms generally that have bristles or setae are considered taxonomic phylum Annelida. For earthworms with each segment comprising of muscles and bristles. This trait serves the role of the anchor while burrowing the soil, or to anchor themselves to the ground when a bird tries to pull them away.

This is often done by the earthworm stretching in and out by contracting and pushing its body forward to get a hold of the earth with its setae.