The hummingbird is taking advantage of a sapsucker's work. The sapsucker has removed some bark from a willow stem, a little at a time. As a result the willow oozes sap from the 'wells.' Several other species also enjoy the willow sap. At the top of the wells a tiny ant sips on the left side of the stem and a female rufous hummingbird hovers as she sips. Three hummingbirds were regular visitors.