This Yellow-bellied Sapsucker is clinging to a tree in our yard. Both male and female sapsuckers have red on the tops of their heads but only the male has a red throat. Sapsuckers drill neat rows of rectangular holes in the bark of trees. In spring, when the sap starts flowing, these holes get filled with sap which attracts insects. The sapsuckers, and early-arriving hummingbirds, visit these trees regularly for the sap and the insects.