Histograms of observed overlap for the <i>D</i> index (Broennimann et al. 2012) between winter and the reproductive season (red lines) data for Baird’s sparrow with the null model (gray bars) for the niche similarity test.

The histogram corresponding to the niche similarity of the winter niche in the reproductive zone (right) and the similarity of the reproductive season niche in the wintering zone (left).