Detection of sap accumulation in the paper birch (Betula papyrifera) by the Yellow-Bellied Sapsucker (Sphyrapicus varius)

Background/Question/Methods

The Yellow-Bellied Sapsucker, Sphyrapicus varius, is a double keystone species, which plays an important role in the mixed hardwood forest and boreal forest of North America by providing cavities, as well as feeding sites, for many other organisms in the forest. S. varius feed on tree sap as a primary source of food, and has a strong preference for the sap of the paper birch, Betula papyrifera. It has been suggested that S. varius farm their own sap by girdling the phloem of the trees in which it feeds on, and later on it can detect sap accumulation due to the previous girdling. I tested the sapsucker ability to detect sap accumulation by comparing differences between the height of their feeding sites in artificially girdled B. papyrifera trees and control non-girdled B. papyrifera trees.

Results/Conclusions

In this study I determined that S. varius is able to detect sap accumulation. The yellow-bellied sapsuckers made their feeding sites, or sapwells, above artificial girds on B. papyrifera trees, at significant lower heights than in non-girdled trees (P < 0.0001).