Fig. 7. Logistic regression of the presence of a breeding Wood Thrush on the log-transformed mass of myriapods. The green circles represent the actual presence (1) or absence (0) of a breeding thrush. The blue circles represent the predicted probability of a breeding thrush presence, given the biomass of myriapods. The relationship is significant (P = 0.0361), and predicts the presence of Wood Thrushes relatively well, correctly classifying 74% sites in which a breeding Wood Thrush was present (Table 2). The dashed line represents the cutoff or threshold value: points above or to the right of the line are predicted presences. The green dot at ~ -7.5 represents several sites in which no calcium-rich prey were found.