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Sunday, September 13, 2009

Washed-out Wilson's Warbler


I took a nice little birding trip to the Chico Basin Ranch after work on Friday, spending the night and then birding a cool Saturday at this well-known Colorado hot spot. Besides birding, I enjoyed catching up with friend and fellow Nikon Birding ProStaff member Brian Gibbons, who is running the banding station there for the Rocky Mountain Bird Observatory this fall.

It was a busy day at the nets, with nearly 100 birds banded. Wilson's Warblers led the tall, and among them was a very unusual one that was mostly lacking melanin pigmentation. In birding circles, individuals like this are usually known as leucistic, although the condition may also be called dilute plumage. On a normal Wilson's Warbler melanin pigments darken the cap, wingtips, tail, bill, and legs. Yellow coloration is from caroteniod pigmentation, derived from plants instead of synthesized by the bird. The olive-greenish back of a normal Wilson's Warbler is from a mix of melanin and caroteniod pigments.
So when most of the melanin isn't present, you get a bright yellow bird like this one, with very pale wingtips and tail, a yellow back and cap, a pink bill, and pink legs. When compared to normal Wilson's Warblers (hatch-year female, left, & male, right), you can see the effects of having normal melanin vs. greatly reduced melanin. Below are a few more comparisons vs. a normal hatch-year female.

6 comments:

Connie Kogler said...

How cool is that. Great comparison photos too.

DaveABirding said...

Fascinating. What an interesting effect from the different types of pigment.

Julie Zickefoose said...

'At's not a proper Wilson's warblah. 'At's a canary!

Beverly said...

Beautiful, educational piece that. Thanks Bill!

I’ve heard that greatly reduced melanin renders feathers much weaker and susceptible to much worse wear and tear. Remember the Golden Eagle found down this way; poor thing was a mess…and also leucistic. A beautiful bird as it regained its health in Pueblo…but I wonder how it’s fairing on release. Much of the problems it had were attributed to the lack of melanin…according to the woman who helped the bird back to health.

I enjoyed the shot of the outstretched wings…it appears you can actually see through the wing’s feathers to the feathers below it. That can’t be good.

Good work…as usual. Thanks again.

inchirieri apartamente cluj said...

Really nice pictures, and a great article. I never knew about this. I haven't seen a leustic bird before, or at least I haven't realised than that is something wrong with its plumage.

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This is beautiful... This is beyond awesome... wooow it is just stunning and I LOVE IT !! It is an honor to see and read this