[keithric]

Found a great spot for Common Mergansers here in Kelowna, then, in editing for posting learned a couple of things: how to tell juvenile females from adults (the white face bar above the lower mandible indicates a juvie), and that some of these birds have a yellow ringed eye and some don't. No doubt there's a simple explanation for this, but I don't know it and didn't find a quick explanation with a Google search. Any authorities out there who can help with this?

The photos below illustrate what I'm writing about:

(Not the best shot, but we can clearly see the difference in the eyes of the birds.

Common Mergansers - juveniles

Less of a face bar here and no yellow eye ring:

Common Merganser - 4

These youngsters where cruising downstream when one nipped the other and caused a kerfuffle
whose aftereffect is still visible in the roiled water.

Common Mergansers - 5

Both juvies above have yellow eye rings.

Looking forward to your help!!

[birdergirl]

Hi Keith,

These are great shots!

The reason the one bird has a black eye with a little bit of white under the eye is because it is a female in non-breeding plumage. The ones with the yellow-ringed eyes are juveniles they also have the black edged white stripe which is noticeable in your great photos.

Hope this helps!

Cheers.

[Fancy]

It's sort of the same with Hooded Mergansers. If you see a Hoodie with yellow eyes, even if it looks like a female, it's a young male. Females have dark eyes.
I found that out after I saw a merganser with yellow eyes and splashes of white on either side of it's face, like a female Bufflehead. I even wondered if it was a cross between a merganser and a Bufflehead, until someone told me that it was likely a juvi Hooded Merganser molting into adult male plumage.

[wendylou]

Super good information! thanks Birder Girl and Fancy for sharing.