Subspecies run rampant

I have a strong interest in species with much regional variation, which usually correlates with a high number of subspecies. No species in North America represents this type of variation than the Song Sparrow. The exact number of subspecies of Song Sparrow seems to vary between 24 and 52 according the the wiki list of subspecies. 10,000 Birds has written a fun post on Song Sparrow's many subspecies here. Check it out.