Saw my first creeper (at right) at Montrose today. He's after the flies and other inverts that are attracted to the sap flowing from the tree. Yellow-bellied sapsuckers are woodpeckers that drill shallow holes in the trees to lap up the sap. They are considered to be "keystone species" because they provide so much food for invertebrates, birds, and other animals.
The sapsuckers (below) are on their way up to Northern Wisconsin or perhaps Canada and some overwinter as far south as Panama :D