科学美国人60秒:Woodpecker Head Bangs Communicate Info

[Pretty bird song]

Some birds produce beautiful songs.

[Woodpecker drumming]

Woodpeckers are not among them. The most familiar sound they make is when they tap on tree trunks with their bills to produce what’s called “drumming."

"This drumming that they show is essentially them kind of slamming their head against a tree at remarkable speeds.” Wake Forest University biologist Matthew Fuxjager.

“Some of the woodpeckers will use this kind of drumming-type maneuvering to excavate a nest, they'll make little caches in a tree to store food, or some of them will actually forage that way. But then they also use it for this social signal."

Fuxjager’s team broadcast the pre-recorded sounds of head slams to mated pairs of downy woodpeckers in the woods nearby. They discovered that there's a lot of information communicated in the drumming.

For example, woodpeckers that produce shorter drums are probably kind of wimpy, and easy to beat in a fight. But if a drum is longer, the challenger might be advertising itself as a stronger, tougher bird, one that's a bit harder to fend off.

And after hearing recordings of long drums, pairs of birds begin to coordinate the defense of their territory. They don’t bother with such behavior after short drums. [Eric R. Schuppe, Gloria D. Sanin and Matthew J. Fuxjager, The social context of a territorial dispute differentially influences the way individuals in breeding pairs coordinate their aggressive tactics, in Behavioral Ecology and Sociobiology]

The researchers think that this kind of coordination might have evolved because woodpeckers invest so much time and energy carving out their nest hole in a tree. If they were kicked out and had to start over, they might not get a chance to reproduce and fledge their offspring. By responding only to more realistic threats, woodpecker pairs can conserve energy to be expended at the hard work of raising their headstrong chicks.

—Jason G. Goldman