Twenty-five different species of cavity nesting birds reside in Sonoma County. Each functions as a piece of a larger puzzle, and are all vital to the long-term sustainability of the biodiversity and ecosystem function within Sonoma County.

All birds have specific roles within their natural community or ecosystem. For example, acorn woodpeckers play a significant part in the dispersal of various species of oak trees, upon which they depend for food and nest cavities. The oak trees provide acorns (food) and cavities (nest sites) for the woodpecker, which in turn helps to spread acorns throughout the area. Each species benefits from the presence of the other. Owls hunt nocturnally for various species of rodents; and help keep their populations from becoming too large. Violet-green and tree swallows consume insects almost exclusively, which can serve landowners by preventing localized outbreaks of pest species, such as mosquitoes.

Removal or decline in population size of even one of these species may have effects that are far reaching, although it may take some years before these effects are expressed in ways that humans can recognize. For example, woodpecker populations may decline if not enough snag trees are left standing for them to excavate. This could lead to a decrease in cavities available to other species of cavity nesters and subsequently their populations would undergo declines. These types of population changes may take many years to express themselves and possibly longer to counteract.