Table 3.
Results of logistic regression of Wood Thrush occurrence on environmental variables
Variable | Est. param. | Wald χ2 | Pr. >χ2 | Std. est. | Odds ratio |
---|---|---|---|---|---|
Intercept | 2.82 | 0.63 | 0.429 | ||
FC1 | 0.38 | 1.80 | 0.180 | 0.21 | 1.46 |
FC2 | −0.47 | 10.03 | 0.002 | −0.17 | 0.63 |
FC3 | 0.26 | 6.54 | 0.011 | 0.14 | 1.30 |
FC4 | 2.47 | 6.53 | 0.011 | 1.26 | 56.18 |
FC5 | 0.94 | 15.37 | 0.000 | 0.52 | 2.55 |
FC6 | 4.03 | 6.73 | 0.010 | 1.90 | 2.56 |
PC1 | −6.12 | 5.01 | 0.025 | −2.31 | 0.002 |
PC2 | −0.11 | 0.15 | 0.696 | −0.05 | 0.90 |
pH | −0.82 | 1.59 | 0.206 | −0.28 | 0.44 |
Trend | 0.02 | 0.10 | 0.749 | 0.05 | 1.02 |
FC4 × pH | −0.42 | 5.76 | 0.016 | −1.19 | 0.66 |
FC6 × pH | −0.67 | 6.46 | 0.011 | −1.73 | 0.514 |
PC1 × pH | 1.27 | 6.61 | 0.010 | 2.65 | 3.560 |
FC1 × PC1 | −0.73 | 4.93 | 0.026 | −0.47 | 0.483 |
FC5 × PC1 | −0.76 | 15.54 | 0.000 | −0.49 | 0.468 |
FC6 × PC1 | 0.72 | 5.13 | 0.024 | 0.37 | 2.064 |
Trend × FC1 | −0.15 | 6.84 | 0.009 | −0.39 | 0.863 |
Trend × FC6 | 0.22 | 9.83 | 0.002 | 0.54 | 1.242 |
Trend × PC2 | 0.12 | 4.90 | 0.027 | 0.24 | 1.128 |
Est. param., estimated parameter; Std. est., standardized estimate; pH, pH of the top 5 cm of soil; Trend, natural log of estimated abundance of Wood Thrush at any site; AIC intercept only, 841.792; AIC intercept and covariates, 761.130. FC1 reflects landscape-level forest fragmentation; FC2, coniferous dominance; FC3, patch size and distance-from-edge; FC4, deciduous shrubs; FC5, sapling layer; FC6, decreases with increasing altitude and decreasing canopy height (22). PC1 represents acid ion deposition; PC2, calcium and ammonium deposition (see Tables 1 and 2).