The conservation of forests in Ontario is reliant on the determination of their significance and whether or not a proposed land use will have a negative effect on the functions of the forest. This research uses the habitat requirements for interior songbirds as a means of developing evaluation criteria for determining the relative significance of forests in the landscape. The results illustrate that forests determined to be significant based on the evaluation criteria cannot sustain development of any form without negatively impacting on their function for interior songbirds. The method developed in this research can provide agencies with a means of identifying and prioritizing forests for preservation, a defensible basis for developing conservation policies, and a method for allocating resources for field work and conservation initiatives.