Table 2. Performance of logistic regression models at predicting presence of a breeding Wood Thrush at a study site, given either the biomass of calcium-rich prey, without slugs, or the biomass of myriapods. The measures of performance are based on the confusion matrices tabulating actual and predicted presences (Guisan and Zimmermann 2000). Cohenís Kappa measures the improvement in number of correct classification to the above the number expected to be correctly classified by chance (Cohen 1960). Area under the curve values (AUC) were computed from receiver operating characteristic curves (ROC).

Predicted =

Predictor
Present
Actually Present

Absent
Actually Absent

Present
Actually Absent

Absent
Actually Present

Present Correct
Absent Correct
AUC
Total % Correct
Cohen % Kappa










Calcium-rich Invertebrate Biomass
15
9
10
4
0.789
0.474
0.65
63.2
26.3










Myriapod
Biomass
14
9
10
5
0.737
0.474
0.69
60.5
21.1