Keeping the beat of the woods with their percussive knocks, Picidae, the woodpeckers, are distinctive birds with long beaks well-adapted to forage for food.
A male Red-bellied Woodpecker (Melanerpes carolinus). Photo by Jacob Gorneau.
There are four main types of woodpecker tongues, which are tailored to the primary food sources of woodpeckers.
1. Woodpeckers like the Northern Flicker, have tongues with “flattened tips,” according to The Cornell Lab of Ornithology. The “flattened tips” allow the Northern Flicker to catch more ants and other small insects with their tongues as they feed on the ground.
The “Yellow-shafted” Northern Flicker (Colaptes auratus auratus) is a very distinctive brown woodpecker. This is a female, identifiable by the lack of a red malar, or “mustache.” Photo by Jacob Gorneau.
2. The Cornell Lab of Ornithology states, “Sapsuckers have brush-like tongues that hold the sap of trees by capillary action.” Capillary action is a process in which water does not need the help of, or sometimes goes completely against, the force of gravity because the adhesive attraction between an object and the water molecules is greater than the cohesive attraction of the water molecules to themselves. Plants would be unable to exist if it weren’t for capillary action, as this process is necessary for the transmission of water from the roots of a plant upwards to the rest of the plant. The xylem allows the water to adhere to its surface, and as other water molecules follow it as a result of cohesion, water is thus drawn up a plant.
The Yellow-bellied Sapsucker (Sphyrapicus varius) is one of a number of woodpeckers that have a specialized tongue to catch sap from trees through capillary action. This individual is a male, characterized by the red crown and throat. Photo by Jacob Gorneau.
3. Woodpeckers that feed on insects in cracks of trees “usually usually have longer tongues with bristles concentrated at the tip,” according to The Cornell Lab of Ornithology. The bristly tips of the tongue allow the woodpecker to more easily catch the insect as it travels within the bark of the tree.
This female Downy Woodpecker (Picoides pubescens) is characterized by the lack of a red patch on the back of the head. Photo by Jacob Gorneau.
4. Woodpeckers known to produce large holes in trees, such as the Pileated Woodpecker, “have shorter tongues with spear-like tips bearing backward-facing barbs,” according to The Cornell Lab of Ornithology. Since the Pileated Woodpecker and its relatives have such large beaks designed to chisel huge holes in trees, a long tongue is not necessary for reaching food.
This male Pileated Woodpecker (Dryocopus pileatus) is characterized by the red malar, or “mustache.” Photo by Jacob Gorneau.
With all of this woodpecking, how does a woodpecker avoid serious head trauma?
Woodpeckers can peck wood with 1,000 times the force of gravity—a g-force so powerful just 10% of that force is highly likely to result in human death. Many woodpeckers have thick, spongy bone in their skulls to provide maximum shock absorption. To keep their eyes in place, woodpeckers have a unique third eyelid. They also have strong neck muscles to help absorb the shock. Woodpeckers have minimal cerebrospinal fluid, which is the liquid which surrounds the brain and spinal column. Consequently, the skull is able to fit around the brain with little space for mobility. Humans have a lot of cerebrospinal fluid—our brains are practically floating—and are thus unable to absorb large amounts of head trauma. According to the scientific journal Science China Life Sciences, the beak of woodpeckers may also be able to bend a little, further diverting the initial shock from the brain. While they are pecking, Samantha Hauserman explains, “Woodpeckers have a special bone that acts like a seat-belt for its skull. It’s called the hyoid bone, and it wraps all the way around a woodpecker’s skull. Every time the bird pecks, the hyoid acts like a seat-belt for the bird’s skull and the delicate brain it protects.” Woodpeckers’ advanced adaptations provide valuable information which could be used to make more efficient head protection for humans in the future.
How can woodpeckers catch insects so easily in tree trunks?
Woodpeckers have saliva that is very sticky (similar to the way anteaters have sticky saliva to lap up insects), and many have barbs on their tongues to further latch on to insects.
What is a woodpecker doing if it appears to be “pecking” without an intent of finding food?
The woodpecker is likely attempting to establish territorial boundaries and may also be trying to call a mate. This is known as “drumming.” Woodpeckers drum because they do not attract mates or establish territory with their calls, and must use their utility tool—their beak!
How do woodpeckers keep balanced on trees while they pecking?
Woodpeckers have zygodactyl feet, which means they have two toes in front and one in back, in the shape of an ‘X’. This helps them easily climb up trees and also maintain stability while they are pecking. Additionally, the stiff feathers of the tail are pushed against the tree for more balance.
The Acorn Woodpecker, Melanerpes formicivorus, is common in California chaparral habitats. Seen at Lake Cachuma Park. Photo by Jacob Gorneau.
Next time you see a woodpecker, admire it not only for its lovely appearance but also for its well-suited adaptations which enable it to have such a unique behavior!
Bibliography
- Hauserman, Samantha. “Why Don’t Woodpeckers Get Headaches?” ASU – Ask A Biologist. 23 Jan 2012. Web. 3 Jan 2014.
- Holtz, Aliza. “How Does the Woodpecker Peck Wood?” Friends Committee of the Fort Tryon Park Trust Gazette. Spring-Summer 2008. Retrieved 4 Jan 2014.
- Pappas, Stephanie. “Why Woodpeckers Don’t Get Concussions | Traumatic Brain Injury & Head Protection.” LiveScience. 10 April 2012. Web. 3 Jan 2014.
- “Woodpecker Biology and Behavior: Biology | Drumming | Diet | Roosting and Nesting | Foraging.” Cornell Lab of Ornithology. Web. 3 Jan 2014.