By Dr. Becker
Have you ever wondered how woodpeckers communicate? They don't sing like other birds. Instead, they produce a hammering noise known as drumming, which is used to "talk" to other members of their species. This shouldn't be confused with tapping, which is primarily done for feeding purposes.
A woodpecker's bill can easily bore into wood, and its long tongue is covered in barbs or sticky saliva, which allows it to pull out ants, insect larvae and other treats lodged in wood and tree bark.
(When not in use, a woodpecker's tongue, which may be up to 4 inches long, curls around the back of its head, tucked safely away between its skull and skin, according to the Cornell Lab of Ornithology).1
Woodpeckers are known to use drumming to excavate nests, create niches in trees for food storage or for foraging purposes, however woodpeckers drum on hard surfaces, from dead tress to stop signs, to chimneys, even when there's no food present, and this drumming speaks volumes to other nearby woodpeckers.
Long Drums Signal Woodpecker Pairs to Defend Their Territory
Wake Forest University biologist Matthew Fuxjager, Ph.D., and colleagues conducted a study of downy woodpeckers, which are known to be highly territorial. The team played pre-recorded sounds of woodpecker drumming, which was meant to simulate a potential territorial intrusion, to mated pairs of downy woodpeckers
Shorter drumming did not prompt a noted reaction in the birds, likely because the sound's creator was not deemed to pose a significant threat to the birds' territory. On the other hand, when the woodpecker pairs heard recordings of long drums, it prompted them to begin coordinated behavior to defend their home.
The birds within the pair also produce contact vocalizations "in a way that predicts their partner's aggressive behavior." According to the study:2
"We find that, when facing intruders that pose a greater threat, residents adjust levels of aggressive output in response to the number of vocalizations produced by their breeding partner. By contrast, this relationship is not observed when pairs face intruders that pose a relatively lower threat.
Our data therefore provide striking evidence that coordination in defensive tactics depends on the residents' appraisal of the social context, such that fiercer competition is associated with greater behavioral coordination."
Put another way, woodpeckers are able to gauge whether another woodpecker is a true threat or not, and decide to launch coordinated defensive behaviors (or not) based on this information. Fuxjager told Phys.org:3
"Partners will actually coordinate or cooperate with how they fight depending on who they are fighting. 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."
Woodpeckers May Tap Up to 12,000 Times a Day
It's estimated that woodpeckers tap 8,000 to 12,000 times each day, at speeds reaching up to 15 miles per hour, not only to communicate risks of territorial invaders but also possibly as part of their courtship behavior.4
The birds are uniquely suited for this behavior; tiny pockets of air surround their skulls, cushioning and acting as a natural shock absorber.5
And that's not all. Chinese scientists conducted an in-depth study to find out why woodpeckers don't suffer from head trauma,6 and it comes down to a number of factors that absorb shock to their skull. As Mental Floss put it:7
"The bone that surrounds the brain is thick and spongy, and loaded with trabeculae, microscopic beam-like bits of bone that form a tightly woven 'mesh' for support and protection."
The spongy bone is more concentrated in certain areas, including the forehead and back of the skull. Specially shaped hyoid bones, which act as an attachment site for some throat and tongue muscles, also likely play a role.
While the bones are horseshoe-shaped in humans, in woodpeckers they form a sling shape that wraps around the skull, helping to further absorb shock and hold the skull steady.
Woodpeckers' brains, meanwhile, are relatively resistant to concussions, thanks to their small size and shape, which allows any collisions that do occur to be absorbed over a larger area.
Other factors also protect the birds from injury, including a third eyelid (nictitans) that closes immediately before their beak strikes a surface.
This protects the eyes from debris and possible detachment. Intriguingly, research has even shown that woodpeckers move their heads in such a way that their brain and skulls rarely make contact at the same point multiple times in a row. Head rotation is also minimized, lowering injury risk.
Their beaks also help, as the upper and lower beaks, being two slightly different lengths, may help divert the stress of impact from the brain. As Audubon reported, woodpeckers even have a way of dealing with the slight bit of impact that does go to the brain:
"In fact, 99.7 percent of the strain energy is converted in the woodpecker's body, and only 0.3 percent is converted in the head. This small amount of strain is quickly dissipated from the head in the form of heat.
This process protects the brain from damage, but causes temperatures inside the skull to rise quickly, meaning woodpeckers have to take frequent breaks while they're pecking. In this way, the woodpecker's whole body is involved in the fight to protect its brain from damage."8
While woodpeckers excel at protecting themselves from damaging, drumming can cause damage to homes. If a woodpecker is frequenting your wooden siding, hanging a windsock or strips of aluminum foil or reflective tape near the area may deter him.
You can also try hanging a suet feeder to lure the bird away from your house and to a different part of your yard.