page_title: Adaptation
section_title: Woodpeckers
hierarchical_section_title: Adaptation / Suits of adaptations / Woodpeckers
caption_attribution_description: English: A green woodpecker (picus viridis) photographed in Carol Park, Bucharest, Romania Română: O ciocănitoare verde (picus viridis) fotografiată în Parcul Carol, Bucureşti, România
context_page_description: Adaptation is the evolutionary process where an organism becomes better suited to its habitat. This process takes place over many generations. It is one of the basic phenomena of biology.
  When people speak about adaptation, they often mean a 'feature' which helps an animal or plant survive. An example is the adaptation of horses' teeth to grinding grass. Grass is their usual food; it wears the teeth down, but horses' teeth continue to grow during life. Horses also have adapted to run fast, which helps them to escape their predators, such as lions. These features are the product of the process of adaptation.
  The illustration of bird beaks shows an obvious sign of their different ways of life. However, eating a different food also means having a different digestive system, gut, claws, wings and above all, different inherited behaviour. For the major adaptations, what changes is not a single trait, but a whole group of features.
  Adaptation occurs because the better adapted animals are the most likely to survive, and to reproduce successfully. This process is known as natural selection; it is the basic cause of evolutionary change.
context_section_description: Woodpecker adaptations are a good example of how a whole suite of features are needed for a successful way of life.
  The bill: its tip is chisel-like, and self-sharpening by the pecking on wood. The bird uses it to get at grubs under the bark, to widen a hole to make a nest and to signal its territory by drumming. Many of the foraging, breeding and signalling behaviours of woodpeckers involve drumming and hammering using the bill.
  Long sticky tongues grab insect grubs which live under bark.
  The millisecond before contact with wood a thickened nictitating membrane closes, protecting the eye from flying debris. The nostrils are also protected; they are often slit-like and have special feathers to cover them.
  To prevent brain damage from the rapid and repeated decelerations, woodpeckers have evolved a number of adaptations which protect the brain. These include
  small brain size
  the position of the brain spreads the area of contact between the brain and the skull
  the short duration of contact
  the unequal length of the upper and lower parts of their beaks (the lower is longer). This steers the impact force downwards, away from the brain.
  the woodpecker’s brain is held in a skull with uneven, spongy plates that absorb shock.
  woodpeckers have a special hyoid bone, which reaches from their beak, loops over top of the skull to completely surround their brains. This acts to keep the brain in place. It is the movement of the brain inside the skull during impact, more than the blow itself, that causes concussions. If the brain is held in place, injury risks are greatly reduced.
  Woodpeckers have zygodactyl feet. These feet have four toes, the first and the fourth face backward, and the second and third face forward. This foot arrangement is good for grasping the limbs and trunks of trees. Members of this family can walk vertically up a tree trunk. In addition to the strong claws and feet, woodpeckers have short strong legs. This is typical of birds that forage on trunks.
  The tails of woodpeckers are stiffened, and when the bird perches on vertical surfaces, the tail and feet work together to support it.
  The whole system is helped by changes in the brain, nervous system, muscles and ligaments from what was usual in their ancestors.
  Ancestral woodpeckers, which switched to climbing on tree trunks, had ancestral foot and tail structure. This suggests that a change in behaviour, perhaps to get at a better food source, was one of the first things that happened in the chain of events. The way evolutionary novelties start is an important topic.
caption: Green woodpecker: note the beak, the feet and the tail
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