In a recent study, biologists say woodpecker couples decide whether or not they need to defend their territory by assessing other woodpeckers’ drumming abilities. The researchers published their findings in the journal Behavioral Ecology and Sociobiology.

Downy woodpeckers (Picoides pubescens) are small birds that take up a lot of room. Each downy woodpecker couple maintains a territory centered around the tree where they’ve made their nest cavity. These territories are often challenged by lone male newcomers, who then frequently find themselves attacked by two angry birds.

However, some intruders are left alone. Researchers wondered how woodpecker couples determine which birds are worthy of this détente. They suspected that the occupying male and female might decide together after hearing what the new bird can do.

Woodpeckers peck to dig out bugs or to carve out nest cavities into the trunks of trees. But their characteristic jackhammer sound is not from pecking; it’s drumming. Unlike pecking, drumming, which usually takes place on especially loud trees or surfaces, serves a purely social purpose—announcing the presence of the drummer to any potential mates or rivals. And as in the world of human music, some drummers are better than others.

Wake Forest University researchers looking for woodpeckers. Image Credit: WFU/Ken Bennett

The researchers took recording equipment into downy woodpecker territories and recorded intruders’ drumming songs. They then manipulated those songs to make them shorter or longer. They returned to the reigning couples’ territories, played back the songs, and watched to see what the birds would do. They found that longer songs consistently got the birds revved up and ready to fight, as it made them believe there was a strong threat nearby. Meanwhile, shorter drums were more or less ignored. But before each bird acted, it checked to see what its partner was doing.

"Partners will actually coordinate or cooperate with how they fight depending on who they are fighting,” study co-author Matthew Fuxjager said in a press statement. “They size up their opponent and decide whether they need to work together. In short, it means an intruder woodpecker with a short drum is perceived as wimpier, while a long drum signifies a tough guy intruder."