Introduction

Every year woodpeckers excavate a new cavity for nesting. After the breeding season, the abandoned cavity is available to be used by other species that use cavities for nesting and sheltering.

In mixed boreal forest approximetely 40 avian and mammalian species use cavities (view species list). These species form three groups that differ in the way they obtain nesting cavities. Primary excavators can excavate their own cavities. Weak excavators can only excavate decayed wood but also use cavities that are available in their habitat. Finally, secondary cavity nesters are unable to excavate and depend entirely on available cavities.

All these species form a community structured around the cavity ressource. This community structure is called nest-web (see lower, Figure 1). The stability of the nest-web is highly dependent on the availability of cavities. Studies in North America indicate that cavities are mostly excavated by woodpeckers rather than being created by natural decay of trees. Hence, species that depend on cavities (ressource consumers) are highly dependant on excavators mostly woodpeckers (ressource producers). A decrease in the availability of nesting trees and of foraging ressources caused by forest management could have strong repercussions on woodpeckers behaviour, population levels, distribution and consequently on cavity availability. These changes can modify the structure of the nest-web.

Figure 1: Example of a simplified nest-web for mixed boreal forest of Eastern Canada

Press here to see the detailled nest-web of the study area