The role of sucrose concentration and sap flow in the selection of sap-trees by the Yellow-bellied Sapsucker, Sphyrapicus varius varius.

Abstract

Feeding habits of the yellow-bellied sapsucker have been studied for nearly a century. Much research has concentrated on explaining why the birds choose birch trees over other species in the late summer months. It is thought that birch is a more rewarding food source because it has a higher sap flow and a relatively high sucrose content. In this study I used both observational and experimental data to try to discover how these two factors influence the sapsucker's choice of individual birch trees over others of the same species. I found that while the amount of sap present at sap-wells is highly correlated with sapsucker activity, the actual sugar content of the sap is unimportant.