Earl Rubin — July 11, 03:03PM
beak color variability within a species
I had a pair of evening grosbeaks here near Winchell Lake AB yesterday, 10 July. The illustrations in the bird book show individuals with light / tan colored beaks while the individuals I sighted had beaks that were black. Is variability in beak color common? Is it age related, a function of local diet or genetics of the local population?