Downy Woodpecker (left) and Hairy Woodpecker (right)
These two similar species are found across the continent. There is some evidence that the smaller Downy Woodpecker has evolved coloration to match the Hairy Woodpecker because it benefits from being mistaken for the larger, more dominant species.
■ Why don’t woodpeckers get concussions? Mainly because their brains don’t weigh very much and are oriented to absorb impact from the front, unlike our brains, which are more massive and oriented to absorb impact from below (like jumping). Woodpeckers have several other adaptations that reduce the impact. Their lower mandible is slightly longer, striking the wood first and transmitting the force through the lower jaw rather than into the skull. A layer of spongy bone at the base of the upper mandible helps cushion any impact there. They always hammer their bill straight into the wood, so the forces are always in the same direction.
The skull and brain of a human and of a Pileated Woodpecker
■ A nest is very close quarters for four or more young birds, and managing the waste products of those growing babies is critically important. One remarkable adaptation of nestling birds is a big help in this effort. At the end of the young bird’s intestines just before defecation, a gelatinous mucous encases each white-and-black dropping in a fecal sac. The baby bird produces a neat “packet” that the adult can pick up and carry away. Newly hatched baby birds instinctively defecate immediately after being fed, and the adults instinctively wait for the fecal sac and fly away with it, scattering the evidence up to 100 feet from the nest. The primary purpose of this is probably to keep the nest clean, but scattering the droppings also helps to avoid an accumulation that could give away the location of the nest.
A Hairy Woodpecker with a fecal sac