Everyone of these birds appears to be a female or juvenile goldeneye; however, the steepness of the forehead and the relatively short bill suggests to me that these are all Barrow's Goldeneyes. Where did you take this photo? Was it in the northern Rocky Mountains? Maybe someplace like Yellowstone or the Grand Tetons where the goldeneyes are all Barrow's? The location would help with the identification. Thanks
@birdsandbats That's very true of females during the breeding season, but juvenile birds (which I suspect most or all of these are) would have dark bills and adult females after the breeding season have mottled orange and gray bills. If this flock had any adult female Common Goldeneyes, we would expect to see a number of birds with orange bill tips, but I don't see any with orange on their bill tips. That leads me to conclude that this is a flock of juvenile birds and a few of them are transitioning from dark eyes to yellow eyes. Barrow's Goldeneye is the only species of Bucephala that nest in and around Yellowstone and is the most likely species in the park from April through November. Also, I lean heavily on the very steep forehead profile and short bill, which indicates Barrow's Goldeneye.
@zoo_sipsik Thank you, that would strongly suggest that these are juvenile Barrow's Goldeneyes because that is the species that breeds in the park and the only goldeneye that's present from the mid-spring through the mid-fall. Thank you for providing the location!
I don't want to come off as being too pushy. If people are more comfortable calling them Common Goldeneyes, I'm good with that. We all tend to see different characteristics in photos and I can't assume that I'm correct. Thanks!
Just barely avoiding cross-posting with @Summer Tanager. I had also been under the impression that bill color was a consistent identifier for females, 30 minutes of researching female goldeneye identification has shown otherwise! As it happens I've only seen Barrow's in winter and spring.
I'll defer to @Summer Tanager's ID on this, I'm not confident enough to issue my own but their logic makes sense.