Unexpected Hummingbird

UPDATE: we have heard back from a hummingbird bander who has identified the bird as an immature male Rudy-throated hummingbird. Hope he has survived the recent cold weather and this was jsut a refueling stop on his way to warmer climes. It's been a great experience learning more about hummingbird identification.

This past weekend my wife saw a hummingbird in our back yard. It is exceedingly late for our normal ruby-throated hummingbirds to still be migrating through. So maybe it is one of the selasphorus genus that sometimes winter on the east coast. But we are struggling to come up with a definitive identification. Any thoughts are most welcome and I'll post updates as we get them. So far we have a a few people suggest that it is a late ruby-throated, and at least one thinking it is a rufous hummingbird.

Here is my wife's write-up and thoughts on what species it might be.

Here is what we noticed:
-buffy wash on sides, meeting in a line across the chest
-grayish spotting on throat; together these give an impression of a double necklace
-back is all green with no observable rufous
-did not get views of splayed tail; no rufous on closed tail; upperside of closed tail gives consistent impression of a white terminal band with a black band above it.
-tail is longer than wings, but just a little bit
-bill is yellow - just kidding - it's covered in a thick coating of pollen, really pretty cute!
-face pattern has white chin and dark above that: white spot behind eye, dark smudge in front of eye, dark smudge behind/below eye, no white above the gape
-apparent dark streaks on green head, but we think this is no so much a field mark as the dark spaces between the feather tracts, since the bird seemed to be holding its crest feathers erect the whole time
-two thin lines of yellow or buffy above and behind the eye.  Again, not sure if this is actually a field mark (some selasphorus have an "orange" eyebrow line) or just more pollen

But what species (or even genus) is it?  Our field guides do not show any dark marks on the throat for a ruby-throat, but then looking online, I did see some photos of immature males with it.  Apparently this can be the immature gorget feathers just beginning to come in.  No rufous coloring seems to suggest it is not Allen's or Rufous, but apparently it can be hard to see on some individuals.  The tail has us really stumped; all the selasphorus (and ruby-throated too) have white on some of the outer tail feathers but not the central feathers.  In images I can find of selasphorus, at least some dark shows at the terminal end of the middle of the tail.  The only images I can find with the appearance of an all-white terminal band are ruby-throats.  I don't know if this is because the outer tail feathers are longer than the inner ones, maybe?  On the other hand, images of ruby-throats seem to have the tail sticking out farther compared to the wingtips than on this individual.  The relatively shorter tail seems better for immature Rufous or Allen's (or even Calliope, which would also be consistent with lack of rufous on the back, but in that case the tail is supposed to be actually shorter than the wings).  The face pattern does not have the extra white above the gape that a Calliope should have, but the white behind the eye and dark in front appears to be common to all of these species.  An expert could probably tell more by size, shape and bill length, but we are not experts, with very little experience identifying hummers, so help would be much appreciated!

More photos at http://www.pbase.com/gbheron/2014_hummingbird.