Burly beefcake or piece of cake?

Contrary to popular thought, woodpeckers don’t just drum trees in search of food or shelter. In fact, woodpecking is an effective, albeit excessively loud form of social communication. It may, for example, be used to announce mating availability, announce presence and ownership of a territory, or even stake a claim to a new (possibly occupied) territory.

Downy woodpeckers, or Picoides pubescens, are particularly territorial little aves. They are easily able to detect individuals who encroach on their established territories, as they make no attempt to curb their blatant advertisement.

But, how breeding pairs of the downy woodpecker react to the intruder depends very much on how much of a threat they perceive it to be. And the way they perceive this is by the intensity of the intruder’s drumming.

Just like how humans (after one too many at their local) size eachother up by height, bulk, or exceptionally chiseled musculature, woodpeckers use the intensity and length of their opponent’s drumming as toughness-cues. Long, sustained drumming is perceived by breeding pairs to be made by a strong, brawny individual, and often prompts a coordinated attack response to fend them off. Shorter, less intense drumming, on the other hand, is perceived by breeding pairs to be made by a pushover, to which duos don’t even bother to respond.

Sizing up their opponents in this way helps the birds conserve energy and mount the best and most efficient kind of defense response. No point wasting energy on inferiors, right?

VP

References: http://bit.ly/29bBaqZ (paywall access) Image credit: Kelly Colgan Azar (https://flic.kr/p/dWf1fR)