Is this an immature male Hooded Merganser

[smittyone@cox.net]

Seen this afternoon in NW Missouri.  This pair of Hooded Merganser stayed together.  One clearly looks like an adult female.  The other one sortof looks like a male.  But I've only seen adult males.  Is this one an immature male, or an eclipse male? 

[DLecy]

"Immature male," I think, is the safest term here. There are many aspects of Hooded Merganser molt, from juvs to adult especially, that are not understood well.

Edited March 20 by DLecy

[IKLland]

7 minutes ago, DLecy said:

"Immature male," I think, is the safest term here. There are many aspects of Hooded Merganser molt, from juvs to adult especially, that are not understood well.

I’ve been told that on a non adult male or juvenile, a pale(yellowish) eye means immature male, and a dark eye means female. But if these birds in the photos  aren’t both immature males, then I guess that’s not true.

[Colton V]

With the all dark bill and pale eye I think the female-looking one should be an immature male too

[smittyone@cox.net]

I was not aware of the eye color thing.  And didn't notice the bill was black on both birds.  I learned something, beside to pay better attention.

That being said, since these both seem to be immature males (I've never seen immature Hooded Mergansers before), why is one so much different than the other?  

[IKLland]

45 minutes ago, smittyone@cox.net said:

I was not aware of the eye color thing.  And didn't notice the bill was black on both birds.  I learned something, beside to pay better attention.

Beware, I said that I was told about the eye color thing. I didn’t say it was true, and I also stated why I think it maybe false. If anybody here knows anything about this, let us know. 

[RobinHood]

9 hours ago, IKLland said:

I’ve been told that on a non adult male or juvenile, a pale(yellowish) eye means immature male, and a dark eye means female. But if these birds in the photos  aren’t both immature males, then I guess that’s not true.

I think it is basically true but may not be that helpful as it takes some time for the colour to completely transition (as in these birds), with adulthood being in summer. The lighting can also affect the apparent colour of the eye.

This is an immature male in February, the eye is no longer a dark brown but not that helpful for ID.

This is just my personal experience.

[smittyone@cox.net]

Follow-up question.  Will males always have a black bill and females always have a two-tone bill regardless of age, respectively?

[Charlie Spencer]

I’m getting way too much enjoyment from this discussion. 

[IKLland]

54 minutes ago, smittyone@cox.net said:

Follow-up question.  Will males always have a black bill and females always have a two-tone bill regardless of age, respectively?

Just based on going through photos on Merlin and eBird that have the age and sex labeled, that seems to be true, but I could be wrong. As @DLecy said, there’s much to be learned here.

[smittyone@cox.net]

I think these excerpts from different sources should add some (helpful?) information.

From Animal Diversity Web;

The males iris is bright yellow, while the iris of females and immature males is duller brown. (Dugger, et al., 1994)

From Wikipedia (not my favorite source).  At least the 2nd part provides a source;

During the nonbreeding season the male looks similar to the female, except that his eyes are yellow and the female's eyes are brown.

First winter birds differ from adult females in appearance in that they have a grey-brown neck and upper parts; the upper parts of adult females are much darker — nearly black. Furthermore, the young birds have narrower white edges to their tertial feathers than adults do. Females of all ages are dark-eyed, whereas in males the eyes become pale during their first winter. (Vinicombe, Keith (2002). "Time for a rethink." Birdwatch 119:16-7)

Smithsonian National Zoo and Conservation Biology Institute does describe the bill colors between males and females, but doesn't distinguish if this is throughout life, or just in adults.

[smittyone@cox.net]

Last excerpt.  This one is from Birds of the World (yes, I bought a subscription).  In regards to other, non-plumage ID features of Hooded Merganser; 

IRIS

In hatchlings moderately yellowish brown (Nelson 1992a). In females iris brownish buff or brownish olive. In males iris similar to females in first cycle, becoming bright yellow in adults. Color can be used to sex Definitive Alternate birds in the field.

BILL and GAPE

In hatchlings upper mandible brownish slate; lower mandible, lamellae, tomia, and base of bill at commisure yellowish pink to light orange; nail reddish brown, pinker at tip; upper egg tooth pale dull yellow, yellowish or pinkish white; lower egg tooth yellowish white, translucent and scale-like. First-cycle and older female with upper mandible blackish green with orange edge; lower mandible muted orange or yellowish. First-cycle male with bill brownish green with orange edge, becoming darker in spring; Adult male with bill black, duskier and paling to yellowish at base in Jun-Sep.

Based on this info, I believe both birds are immature males, with one a little farther along in it's molt.  The yellow eyes also verify them both as males--darkish eyes in males turn yellow early on, whereas female eyes are always dark.  Regarding the bill, male bills turn dark early on, while female bills never turn dark for both upper and lower mandibles.

Correct me if I'm wrong, but I believe Birds of the World is supposed to be pretty much THE definitive source.  The downside to this resource is how many words I had to look up!

 

Thanks everyone for your input on this. 

 

[Birds are cool]

Great photos @smittyone@cox.net!