Decisions about habitat conservation are often based on estimates of population size, and therefore rely on the assumption that population abundance reflects habitat quality and better fitness. However, some species can be as, or more, abundant in low-quality than high-quality habitats, where resource availability and fitness are low. Decisions based solely on abundance therefore run the risk of reducing the availability of good-quality habitats because of the assumption that habitats with low abundance are expendable. To test whether amphibian abundance is positively correlated with fitness in the boreal forests of northwestern Ontario, I compared the abundance and body condition of amphibians in logged and unlogged mixed and conifer forest. Body condition and abundance of adult American toads can be used as an index of habitat quality. Alternatively, wood frogs and juvenile American toads may be subject to interference, competitive differences or perceptual constraints, and the use of their abundance as an index of habitat quality is ill-advised without further work on resource selection, population recruitment and intraspecific interactions in the boreal forest.