Fig. 4.

Simulated bird concentrations over time at an ALAN source (solid lines). Vertical dashed lines indicate time to steady-state stabilization. Model parameters a and κ are described in SI Appendix, Eqs. S1 and S2, with parameter σ fixed at 1,500 m (SI Appendix, Table S1). Model 1 represents the best fit to the observed patterns at the installation, but this model is still conservative in that higher-than-predicted concentrations of birds occurred in certain periods. In general, bird concentrations at the installation could only be explained by including directed flight toward ALAN for disoriented birds (κ > 0). These results support our observations that birds were disoriented by and attracted to the installation.