On Jan 23, 2013, at 11:18 AM, Hank Karen wrote:

> What is the explanation for the colors of this Mallard?
>
> http://www.flickr.com/photos/ljcouple/8408211565/

Leucism? It's more a description than anything else.

Kelly Cassidy more precise explanation is close but I think the production of pheomelanin is also reduced in these birds. Otherwise the bird would be lighter than "normal" Mallards but the hue would be closer to reddish-brown (e.g. pheomelanin is what makes ginger people ginger ... you need to dilute it and add eumelanin to make brown). These birds really seem to be sandy in color (a very light brown).

Recall that black Mallards do have eumelanin fully turned on in their feathers so there can't be a huge amount of eumelanin in a normal female Mallard plumage (otherwise they wouldn't be brown).

Find a copy of Geoffrey E. Hill's "Bird Coloration" for more info. It's aimed at birders and improving their understanding of how bird coloration works.

There has been a rather beautiful looking "sandy" female Mallard at Greenlake over the past couple of years. I beleive I saw the same or a very similar bird (are they that common? or are they just moving around? ) in Portage Bay during this years CBC (in that case it demonstrated that we probably were double counting ducks as they moved between two locations on opposite sides of the Bay unless there were two of them).

One other thing I've noticed about them is the males like them. Clearly leucism doesn't seem to be too much of a turn off. Perhaps it may lead to assortative mating if they like it enough :-)
--
Kevin Purcell (Capitol Hill, Seattle, WA)
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