Redpolls are an interesting study
because of variation between adult males and females and first year
males and females. Four subspecies add to the challenge: two Common
Redpoll subspecies - "Southern" Common Redpoll (flammea) and
"Greater" Common Redpoll (rostrata); and two Hoary Redpoll
subspecies - "Southern" Hoary Redpoll (exilipes) and
Hornemann's Hoary Redpoll (hornemanni).