Field investigations showed that the Ruby-throated Hummingbird (Archilochus colubris) feeds on phloem sap in the northern part of its breeding range. The sap food source is contained in holes drilled by Yellow-bellied Sapsuckers in birch trees. Sap is preferred over nectar in flowers by brooding females. Although the hummingbird is the most incessant visitor, other birds and many insects are associated with sapsucker feeding trees. Sap from trees has 16% sugar concentration and laboratory studies indicated that pollinators can be supported by this food. For hummingbirds tested in the laboratory, total energy consumption remained about the same (0.16 cal/g/hr) while volume and frequency of feeding depended on the sugar concentration of the feeding solution. Hummingbirds and many other pollinators are opportunistic sapivores and nectarivores and their distribution may be significantly affected by active summer feeding trees of Yellow-bellied Sapsuckers.