Separating F Black-chinned from Broad-tailed Hummingbird

[Robert Righter]

This morning while birding the Lair-of-Bear Park a female hummingbird was darting back and forth across a small creek. The two expected hummers for the region would be the Black-chinned and the Broad-tailed. Given the hummers constant motion it seemed impossible to determine if the bill’s length, was long or short, nor if the back color was emerald green toned or dullish, gray green  suggestive for a Black-chinned. From the occasional views of it flicking its tail showed small white spots on each side of the tail, although at times hard to determine. In contrast the tail of the Broad-tailed does have a broad tail its white spots at the corner of its tail are more distinctive. Thus by this definition the humming bird I was looking at was a Black-chinned ??

Anyone else have tips on separating female  Black-chinned from  Broad-tailed.

Bob Righter

Denver, Colorado