Susan Collicott wrote:

"Could she have gotten into something and it's now washing out, showing her
true colors? (as in, she was always light golden tan, but got covered in
gunk?) But that leads me to the question, are there light golden tan & white
Mallards? Could this be a cross-breed? Could she be losing feathers, and
therefore showing more down? Could she be a cross-breed, and could she be
moulting and therefore showing more of her cross-bred feathers? See, I don't
even really know when ducks molt, I'm such a beginner, that I don't know if I
should even contemplate the theories that involve molting."

Susan, sorry for treating your query with a certain amount of humor and
perhaps implied skepticism. I believe you stated accurately what you saw,
but I can't think of any rational explanation for it. I don't really think
that she was getting pale as she got clean, if you saw this change
gradually over a period of days. I would think a duck would be clean as
soon as it went into the water, no matter what kind of mud it was in, and
if it didn't come off with the first immersion, it was on for good.

I would think that at close range you could distinguish between down and
regular feathers. A bird would have to look very ragged for there to be
lots of down exposed; it's normally covered by the contour feathers.
Typically when birds molt you don't see evidence of it on the body, except
when they change color, of course. You can often see pin feathers around
the head, because they are such short feathers that when a couple of them
are lost you can see new ones growing in. But a duck has to be well
insulated, which is why molt is gradual, with only 10% or so (very rough
estimate) of its body feathers growing at once. Wing and tail feathers are
another story; they're lost simultaneously in waterfowl, making them
flightless for a while. In most birds, wing and tail feathers are molted
slowly and sequentially, so the power of flight isn't lost.

Most birds have a complete molt in fall, replacing all feathers. Those
that change color seasonally then have another body molt in spring. Ducks,
however, are rather unusual in the timing of their molts. Adults have a
major body molt in June/July, when males change into "eclipse"
(female-like) plumage and quickly lose their wing and tail feathers, then
they grow them back and become airborne later in summer. They then undergo
another body molt, mostly September to November, when males change back
into their definitive "breeding" plumage. There is molt going on through
the winter in immature ducks but not usually adults.

If the different colored feathers are interspersed, it does sound more like
molt than individual feathers fading rapidly. April isn't molting time for
normal ducks, but I have just about given up on all the domestic and
semidomestic birds that are becoming a larger and larger proportion of our
avifauna. Many of them don't behave quite normally; they're as aberrant as
people can be. Argghh!

Pale tan and white Mallards are common, both of them, I think, bred for
those colors. I don't think a tan Mallard is a hybrid between a white one
and a brown one, but I could be wrong. I've thought the white-patched
birds were such hybrids. I saw a couple of tan females just this weekend
while kayaking near Montlake Fill, and I know there are some at Green Lake.
With Mallards, it seems we are approaching a situation somewhat like Rock
Dove----> domestic pigeon, but in this case with a native species. It
saddens me to see this sort of change.

Keep watching. Maybe you'll figure out yourself what's going on.

Dennis Paulson, Director phone: (206) 756-3798
Slater Museum of Natural History fax: (206) 756-3352
University of Puget Sound e-mail: dpaulson at ups.edu
Tacoma, WA 98416