What a pretty boy....do you know they feed their mate? ......I lived the other twenty years in OHIO and the cardinal is the state bird of the buckeye state.
Well, what I've learned is that the Calliope is very small, smaller than the other hummers that pass through CO and it has an unusually short tail and shorter bill, comparatively speaking. The seemingly popular field-marker for Calliopes is that if the wings extend to the edge or past the tail; it's a Calliope. I learned this when I posted a simply awful little photo on my blog and some guy about went on and on that I needed to post it at a Rare Bird Alert page. It was a funny….
In addition to its short tail, the Calliope doesn't pump its tail the way many others, like the Black-chinned, do. This is a mountain bird (seen as high as 11,000') which likes to perch, and nest, low to the ground. According to Dan True (Hummingbirds of North America) "…this is a clue to recognizing the bird. In the wild, it flies low and stays low, rarely getting above five feet. Attracting this hummingbird with a feeder would best be done with one located no higher than four feet."
Past that…and understanding birds, like people, vary enough individual to individual; it is fairly impossible to discern a female Calliope from a Rufus or a Broad-tailed female, though RT Peterson mentions the female Calliope may be somewhat paler in the buffy-underside area.