Figure 4.

Relationship between thermal niche overlap and relative size differences between congeneric species pairs of Himalayan birds (n = 201 pairs). (a) In the west, thermal niche overlap between congeners was not related to differences in body size in either summer or in winter. (b) In the east, similarly sized congeners segregated in thermal space in winter, but occupied similar thermal space in summer. Bold lines and shaded regions reflect predicted relationships from weighted quasi-Poisson regressions with 95% confidence intervals, respectively. The transparency of each point indicates its relative weight in the regression—bolder points contribute more towards model fit (see Material and methods).