Incompleteness maps of high-z quasar selection using Owl-z, shown as a function of redshift and H_E -band magnitude. Each panel displays the fraction of quasars with P_q<0.1, i.e. quasars misclassified as MLT stars (left panel) or intermediate redshift galaxies (right panel), colour-coded by the percentage of quasars lost in the bin. These maps illustrate the regions of the parameter space where the selection is least complete and help characterise the dominant sources of contamination.