This originally appeared in OBOL, but it may be of interest to Tweeters,
so I have posted it there as well.
>
>
> Most of the ones I see in the winter are approximately white
> with black or gray splotches, though it is true that you can't
> depend on the splotches being in the same places on any two birds.
> Of the two birds that summered in Trestle Bay this last year. One
> closely approximated alternate plumage, the other was a typicical
> winteryish splotch thing.
> I had one at Brownsmead last weekend that was gray.
>
> >
> >
> >
> >As far as I have ever been able to tell, Oldsquaws are not very
> >picky about matching their plumages to the seasons. I have not
> >bothered to do any research on it, but I have seen small groups
> >on occasion in which NONE of the birds was in the same plumage,
> >going by what the field guides would have us believe.
> >
> >--
> >Alan Contreras
> >Oregon Community College Assn
> >1201 Court NE, Salem OR 97301
> >(503) 399-9912
> >
> >
>
> --
> ********************************
> * Mike Patterson, Astoria, OR * Oh, joy... rapture
> * mpatters at ednet1.osl.or.gov * I've got a brain.
> ********************************
>
I had been meaning to reply to this posting but I had forgotten. One
of the reasons why Oldsquaws may appear to be all over the place in terms
of their moult is that their annual moult cycles are rather complex.
First of all, the winter plumage is actually the Alternate plumage on
the Oldsquaw, so if you go out and see one of these nice white, grey and
black males now he will be in alternate plumage. The same is true of the
females of course. Each year the Oldsquaw goes through three cycles of
moult wich gives you the Alternate, Basic and Supplemental plumage. The
pattern is that they moult into Alternate by moulting all of the feathers
except the wings, tail and belly. This happens in September to October
and is retained into May. The flank feathers from the Basic plumage are
retained a lot longer than usual, so that birds are often in full Alternate
but with Basic flanks. The Basic plumage is acquired by moult of all of
the head breast and mantle in April, once again the flank feathers are
retained. In June or July the supplemental moult occurs by moulting some
of the mantle again and now the flanks. The wings and tail will be moulted
at this time. That is the basic story, and there are sex differences in
moult.
Immatures are also complex in their moulting. They moult from the Basic I
plumage to a Supplemental plumage in fall or early winter by moulting the
scapulars. In mid winter they moult all of their feathers except the
flight feathers in their pre-alternate moult. The timing of this moult
is quite variable and probably accounts for the diversity of Oldsquaw
plumages that are observed in the field.

The point of the story is that Olsquaw plumages are downright confusing,
so it is not really unexpected that they can all look different or that
the timing of moults differs between individuals. Part of this may have
to do with how far away they are coming from.

Alvaro Jaramillo
jaramill at sfu.ca
Vancouver, B.C.