Hummingbird with dark belly band??

[Becky Campbell]

I am still trying to learn immature hummingbird identification!!  I have had an individual for the past four days that has a very dark band completely across the belly with more blackish patches below.  Throat is very lightly spotted and chest is white.  Wings approach tail length, head spotted greyish green.  I have not seen any rufous coloration or gotten good view of tail.  Overall impression of proportions/size is black-chinned hummer-ish.  The bird comes in to my feeder briefly and then flies out sight to perch.  Have not had great views of the back.  I have never seen a dark wash extend beyond the sides.  Is this common?  Is the black appearance just a lighting phenomenon?  Is this an immature characteristic?  Which species would show this? 

Becky Campbell

Arapahoe Cty.   

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Arapahoe County, CO