Widely known in North American folklore for its amusing name, this woodpecker creates shallow holes (sap wells) in the bark of trees and feeds on sap that flows into them. Like other sapsuckers, the Yellow-bellied Sapsucker creates elaborate systems of such sap wells and maintains them daily to ensure sap production, defending the wells from other birds, including other sapsuckers. When feeding young, sapsuckers usually forage for arthropods, especially ants, but some of these prey items are dipped in sap wells, perhaps for added nutritional value.
Sapsuckers appear to play an important ecological role in the communities they inhabit. Many animals make use of sapsucker sap wells to supplement their own food intake with sap itself or with insects attracted to the sap. The Ruby-throated Hummingbird (Archilochus colubris) appears to be closely allied with sapsuckers. This humming-bird places its nest near sap wells, follows sapsuckers in their daily movements, and may even time its migration to coincide with that of sapsuckers ( Miller and Nero 1983 ). In addition to drilling sap wells in trees, sapsuckers excavate nest cavities that often provide nesting or roost sites for other species of birds and even some mammals (e.g., northern flying squirrel [Glaucomys sabrinus]) that cannot excavate their own.
The taxonomic complex comprising the Yellow-bellied, Red-naped (Sphyrapicus nuchalis), and Red-breasted (S. ruber) sapsuckers has often been treated as a single species with an east-west pattern of in-creasing amounts of red plumage. The Yellow-bellied Sapsucker, least red, breeds east of the Rocky Mountains; Red-naped Sapsucker breeds in the Rocky Mountain-Great Basin region; and Red-breasted Sapsucker, with its head entirely red, is found along the Pacific Coast. Within this species complex, research has focused on Yellow-bellied Sapsuckers, but the biology of all 3 species is undoubtedly similar (see Walters et al. 2002a ). Major studies of Yellow-bellied Sapsucker include that of Louise de Kiriline Lawrence, working in Ontario ( Lawrence 1967 ), and Lawrence Kilham, working in New Hampshire (Kilham Kilham 1962a , Kilham 1971a , Kilham 1977e , Kilham 1983a ).