I was curious as to why the Flickers would drum on the old bird condo near the suet, and I discovered that the Northern Flicker is a woodpecker, and has some interesting habits.
"Springtime brings the sound of a woodpecker - maybe one like this Northern Flicker - drumming on a hollow surface. Members of the woodpecker percussion band announce their territory and attract mates, as they pound away on metal roofs or gutters. Drilling holes in tree trunks calls for some specialized tools, and the North Flicker has them: big claws, two toes pointing forward and two backward, and a stiff tail to prop itself up". Link
