and P. sindianus Phylloscopus (Willow warblers) Powelliphanta Rhymogona silvatica and R. cervina (the names and classification of these species have changed since the publication suggesting a ring species) Melospiza melodia, a song sparrow, forms a ring around the Sierra Nevada of California with the subspecies heermanni and fallax meeting in the vicinity of the San Gorgonio Pass. Todiramphus chloris and T. cinnamominus See also Dialect continuum, a similar concept in linguistics Intergradation References External links Greenish Warbler Greenish Warbler maps and songs Ensatina salamander , by Peter Hadfield (potholer54) Nova Scotia Museum of Natural History: Birds of Nova Scotia Hybrid Gulls Breeding in Belgium Species Evolutionary biology