Having two (or dimorphic) or more distinct, genetically determined colour morphs within a species, independent of age, sexual, seasonal or subspecific variation 
^Zimmerman, Dale A., Turner, Donald A., and Pearson, David J.; Illustrated by Zimmerman, Dale A., Willis, Ian and Pratt, H. Douglas (1999). Birds of Kenya and Northern Tanzania. Princeton University Press. ISBN0691010226.Cite uses deprecated parameter |coauthor= (help) CS1 maint: Multiple names: authors list (link)
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