Woodpeckers are most known for their proclivity of hammering on trees for food.  Most search for insects (such as termites, flying ants, and some that even pose a threat to live trees) but some species, such as sapsuckers, often seek out tree sap for nourishment.  The entire body of a woodpecker is uniquely designed to both maximize and withstand the impact of these blows.  If a human were to endure just one headbutt against a tree using the same force, in accordance with his / her bodyweight, it would shatter the person’s skull!  The holes excavated by these incredible birds provide refuge for a number of other animals such as squirrels, small owls (screech, pygmy, and elf owls all nest in woodpecker cavities), and a host of other birds!