FIGURE 2.

Trend of the proportion of resightings done per year in winter (Dec–Jan) in a theoretical grid over NW Europe (M2 in main text). Coloured dots represent gridcells with resightings in >5 seasons within the study period. The colour shows the trend of the slope of the proportion of resightings in that gridcell over time, with red being a significant (p < .05) negative slope (−) and orange a significant positive slope; white dots have non‐significant slopes. Slope values are visualized in the bottom panel of the figure, where the colours again indicate the significant trends. The solid black line in the bottom panel indicates a significant increase in the (weighted) slope value from west to east (see text). Dashed black lines represent the 95% CI of the regression. The red location with the black outline (main figure) is Slimbridge, a WWT site and the location with the largest decrease in proportion of resightings over time (slope −0.0166; excluded from bottom graph and analysis). The orange location with the black outline is in the province of Noord‐Brabant in the Netherlands, where the largest increase in the proportion of resightings took place (slope 0.0037)