We have three types of woodpecker in the trees I can see out of my living room window. The Hairy, the Downy and the Pilated, mostly they look that same except the Pilated is a good bit larger. Ocassionally they fly over to the deck and take advantage of the suet I have put out.
The woodpecker has two toes in the front and two toes on the back of its feet, so it can grip firmly, it also has very strong legs to support it while it pecks, up to one hundred time a minute, through bark looking for insects.
The woodpecker's bill is unique among birds in that it has a spongy tissue between its bill and its skull, while other bird's beaks are directly connected to their skulls. The spongy tissue acts a a protective shock-absorber to cushion its brain from damage while it pecks with all its might for several hours.
A woodpecker can even peck through a concrete! I have seen them at stop signs for hours trying to peck through but with no success, also road lights, going for the metal because they can hear the buzz of electricity going through it and think it is an insect. They have extremely sensitive hearing and sense of smell which can detect an insect under an inch of bark.
The woodpecker's tounge is also unique and is extremely long, four times longer than its beak, and not attached to the rear of the mouth like any other species of bird. It is kept coiled around its brain, ready to capture insects hidden deep within a tree trunk.
I have difficulty in believing this was not a planned design but just happened by chance.
Notes taked from 'The Wonders of God's Creation" by Grant R. Jeffrey