What Bird Is That Forum

Over the last few weeks here in Avon, CO there have been some Merganer's I've seen. Don't know if the photos are good enough but trying to determine if I've seen Common, Red-Breasted or a combo of both. Thanks!

I'll call the first three photos as Common. On the neck, there's a clearly defined separation of red and white. I'd expect the split on a Red-breasted to have more overlap and smearing.

The last two probably are Common too but I can't see that field mark as well. I'm not touching that scaup in the last photo.

Pretty sure all are red breasted actually

The head feathers and the white streak between the bill to the eyes had me leaning red-breasted. Photo 3 in particular though seems to have a pretty clear delineation between the red head and white chest which had me second guessing. Photo 2 and 3 are definitely the same bird. The other 3 were taken a couple weeks earlier so probably different birds.

Someone correct me if I’m wrong but I’ve found the absence of a clear white throat to be an easier field mark because the neck to chest demarcation can be misread easily I feel
That and the slender bill point to RBME to me

The clear white throat definitely seems to be the easiest ID from researching what to look for. Unfortunately I don't feel like any of the photos I got show the throat very well so have been trying to use the other features to determine. Like you I'm feeling RBME for all of them. Was hoping maybe one of them was Common so I could add both types the list lol.

Agree with Red-breasted - blocky head, lack of white throat patch, white eye-ring, more upturned bill, lighter brown head. I find the bill thickness quite variable and not too reliable.