Date: 2/23/17 3:42 pm From: Wayne Hoffman <whoffman...> Subject: [obol] More thoughtson the Bingen goldeneye.
First, a quick summary of what I see in my photos.
1. The head does not seem to be in molt.
2. No sign whatsoever of a white medallion, crescent, or intermediate mark.
3. The head was less iridescent than typical of either Common or Barrow's. Some photos showed a little iridescence, not green nor blue-purple, but maroon to reddish purple. [Maroon is typical of Common X Barrow's hybrids.]
4. Head shape is higher-peaked than typical for Common, a bit more like Barrow's.
5. The bill seems smallish for Common, more like Barrow's, but not an easy call.
6 The body/wing plumage, as seen on the swimming bird, appears to be either full adult, or nearly there.
7. The inner secondaries were a bit ruffled or disturbed. They seem to show a bit more black than typical for a Common, but much less than on Barrow's, or on F1 hybrids.
8. No sign of the Black spur that Barrow's has separating breast from flanks.
9. On both species the white panel of the flanks ends near the legs and the rear flanks and under-tail coverts are black.the boundary between the two is slanted, such that the whit extends further posteriorly at the top than at the water line. The angle of this boundary differs between the species, especially when swimming high in the water. On Common the boundary is sharply slanted, often more than 45 degrees from vertical, and on Barrow's it is closer to vertical. on the Bingen bird it is somewhat intermediate, but more like Barrow's.
A. Possibly this is a young bird that has completed or nearly completed its body feather molt but has skipped the head molt. This seems unlikely because the head plumage does not seem worn or faded, and does not seem to be the female-like brown shade of immatures.
B. Possibly this is a hybrid Common X Barrow's. The lack of facial white aside, this bird looks a bit more like a Common X Barrow's Goldeneye than either of the species. Normally these hybrids have a white facial mark that is pear-shaped - essentially the white medallion of a Common pulled up into a point in front of the eye. The upper-wing pattern looks more like Common, but most of the other features seem to show Barrow's influence.
C. Possibly this is a hybrid Goldeneye X something else? The main problem with this is that no other parental traits are obvious. Birds identified as Goldeneye X Bufflehead hybrids tend to have extensive areas of white on the sides of the face. Interestingly, birds identified as Goldeneye X Hooded Merganser hybrids have dark heads lacking both the white medallion or crescent of the goldeneye, and the white crown (some have a few .smll white patches near thier eyes). Evidently each parent provides genes blocking the expression of the other species' white marks. However, these hybrids tend to have larger, rounded heads, and also show the dark arcs separating the breast from the flanks of the merganser parent. They also tend to have longer, lower-profile bills.
D. Possibly this is "just" a Common Goldeneye lacking the medallion. Possibly, but the other features noted above tend to show differences suggesting also Barrow's influence.