Something to consider -; in some duck species, older females can begin to show male plumage traits. So a good option for what you saw was an older female Mallard.
I tried to find sources that talked about this with a bit of a search and came up mostly short - but there was one article that gives a lot of interesting detail [assuming it is all correct] and goes to a further length than I was aware of:
https://www.bbc.com/news/science-environment-40016817 <
https://www.bbc.com/news/science-environment-40016817>
That article points out that unlike with humans, female birds are the gender that has mixed chromosomes - one W and one Z -; Males have two Z. So, all female birds have a Z chromosome that carries all the plumage info for males. The article claims that after a female duck's ovary stops working, there is less pressure to suppress those male characteristics.
But there's more! Apparently sometimes this progresses to the point of previous female birds transitioning to males, complete with the ability to become fertile as males and 'father' chicks.
I saw a couple less-credibly sourced references to male birds [usually chickens] also sometimes transitioning to female - doesn't fit with the chromosome explanation above so it would be a reason to question that if it were true.
Matt Bartels
Seattle, WA
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On Mar 5, 2019, at 6:18 PM, Jeff Kozma <jcr_5105 at charter.net> wrote:
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FYI, young males would not have an orange bill like a female mallard. Their bill would be yellow. Also, first year males are now in full adult breeding plumage by this time of year.
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Jeff Kozma
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Yakima
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<>
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From: Tweeters [mailto:tweeters-bounces at mailman11.u.washington.edu <mailto:tweeters-bounces at mailman11.u.washington.edu>] On Behalf Of Sammy Catiis
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Sent: Tuesday, March 5, 2019 1:27 PM
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To: Jeffrey Bryant <jbryant_68 at yahoo.com <mailto:jbryant_68 at yahoo.com>>; tweeters <tweeters at u.washington.edu <mailto:tweeters at u.washington.edu>>
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Subject: Re: [Tweeters] Intersex Mallard at Black River, Renton
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I'm guessing it's a young male just coming into plumage.. the reason being, that we have two that look identical to that here in Sequim.. unless it's a hybrid.. that might be too.. but for them to look identical, I'm guessing it's something more rooted than a intersex morph.. guessing hybrid of Wigeon.. or just a difficult phase.. IDK When I see more than a handful that look the same, something says it's more natural.
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Sammy
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now in Sequim
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From: Tweeters <tweeters-bounces at mailman11.u.washington.edu <mailto:tweeters-bounces at mailman11.u.washington.edu>> on behalf of Jeffrey Bryant <jbryant_68 at yahoo.com <mailto:jbryant_68 at yahoo.com>>
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Sent: Monday, March 4, 2019 3:18 PM
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To: tweeters
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Subject: [Tweeters] Intersex Mallard at Black River, Renton
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So I've HEARD of intersex birds, especially ducks, but never seen one until today. During a dog walk through Black River Riparian Forest, accessed from Oakesdale/Monster Rd. on western edge of Renton, I had a Mallard with female body and big black splotch on bill, but iridescent green head like a drake, save for buffy-brown cheek. Photos in ebird checklist: https://ebird.org/view/checklist/S53393579 <https://ebird.org/view/checklist/S53393579>
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Not as sexy (pun intended) as that gynandromorph cardinal in Pennsylvania, but still a cool bird to stumble across. Clearly paired with a "normal" male Mallard. If you believe the internet, it is probably an aging female whose estrogen levels are low.
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Jeff Bryant
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Seattle
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jbryant_68 AT yahoo
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Sent from my iPad
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