In the article: Canyonland Roadrunner Captured on Film « Santa Monica Bay Audubon Blog is an article and photo of what many consider of a possible second form of Road Runner, Canyonland Roadrunner. Others believe that they are not a separate form but are a variety of the Greater Road Runner Geococcyx californianus.
Observable differences mentioned in the article include:
“the new bird G.c.sp.nov. overall plumage is a plain, unstreaked gray to blue-gray. Crown feathers extend into a dark, long and flowing crest. Eyes are located at the front of the head, rather than the side, presumably producing improved frontal binocular vision while impairing peripheral vision. The bill is thick and upcurved, giving the bird a permanent amused expression. The neck is extremely elongated and slender, resembling that of an egret more than the nominate G.californianus. ”
Read full article at Canyonland Roadrunner Captured on Film « Santa Monica Bay Audubon Blog.
Natural History Wanderings 
There is also a Lesser Roadrunner, Geococcyx velox, found in arid W. Mexico (s Sonora) to n Nicaragua. Then there are 5 species of Ground-Cuckoo (genus Neomorphus) spread around So. America, which are closely allied with the roadrunners. (Chuck Almdale, writer of the “Canyonland Roadrunner…” cited above.
LikeLike
By: Chukar on April 4, 2012
at 2:30 PM
Thanks for the information. All of it is new to me as I was only aware of what was in the article and Sibley and National Geographic field guides.
LikeLike
By: Sandy Steinman on April 4, 2012
at 2:41 PM