[Tweeters] Williamson's Sapsucker -- abnormal plumage one side

Jeff Kozma jcr_5105 at charter.net
Fri Mar 4 22:00:42 PST 2016

It looks to me that the Williamson’s Sapsucker you photographed/videoed looks like it might have a plumage abnormality where the side feathers that are black/barred/streaked with white have formed along the belly, as well in a bilateral pattern, where it only occurs on the birds right side. This could be a case of bilateral melanism where the side/belly feathers on the right side are darkened abnormally. From the photo and video, it looks like a normal male WISA except for this darkened streaking pattern on the right side and belly. My guess would be bilateral melanism.

Because of the bilateral nature, I first thought it was gynandromorphy, a bird showing both male and female characteristics because this condition occurs bilaterally. But, this bird doesn’t show any female plumage characteristics.

I don’t think this bird is a hybrid, as evidence of hybridization through plumage usually isn’t confined to a specific area. There is generally an overall mix up of plumage characteristics between the two species that crossed and in my experience isn’t confined to one side of the body.

Other than some sort of melanistic condition occurring only on the right side (melanism and leucism often occur patchily or in non-patterns), I’m stumped.

Jeff Kozma


From: tweeters-bounces at mailman1.u.washington.edu [mailto:tweeters-bounces at mailman1.u.washington.edu] On Behalf Of Kevin Lucas
Sent: Friday, March 4, 2016 8:55 PM
To: TWEETERS <tweeters at u.washington.edu>
Subject: [Tweeters] Williamson's Sapsucker -- abnormal plumage one side

Williamson's Sapsucker half-normal plumage

My reward for a nice long hike in the snow today was a Williamson's Sapsucker (WISA) that had yellow only on the left side of its breast. On its center and right breast were black and white markings -- not the black with white wisps I usually see on adult males' breast sides. Its vocalizations and drumming were typical for WISA, and it was calling and drumming with two or maybe three other WISA. In March of previous years I've photographed WISA with unusual black markings in what is usually a solid white wing patch, but this seems like something different is happening -- where plumage on just one side is wacky.

Can anyone provide me with information on what causes this one side color abnormality, and whether there's a term for it? So far my Google searches have landed on albinism and leucism. Maybe it has something to do with hybridization.

I posted a still image frame capture from a movie, along with a movie in which you can hear the characteristic WISA drumming. I apologize for the image shake (superzoom hand held in the cold).
Here are links to the still photo
and to the movie clip
on my Flickr photostream.

Kevin Lucas
Selah, WA

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