Table 2 Estimates from the mixed effects model, showing fixed and random effects, as well as the intraclass correlation coefficient (ICC) for the random effects. The log transformed abundance estimate was modelled as the outcome. Coefficients are exponentiated and p-values given

Fixed effects

EXP(β)

95% CI

P-value

 Intercept

157.83

(125.47–198.41)

< 0.001

 Distance-method vs Chapman

1.35

(1.20–1.53)

< 0.001

 Surveyor B vs A

1.21

(1.07–1.37)

< 0.01

 Survey 2 vs survey1

0.82

(0.72–0.92)

< 0.01

 Subset vs all roads

1.05

(0.92–1.19)

0.48

 Afternoon vs morning

0.80

(0.57–1.11)

0.19

Random effects

Variance

Std. Dev.

ICC

 Working zones

0.14

0.38

0.41

 Residual

0.20

0.45