Michael Price wrote:

"Also, to piggyback a query, does anyone have a relatively foolproof way of
separating female Garganey from female Green-winged Teal with sometimes
equally-strong facial markings? And what's with these female Mallards with
whitish heads and grey stripes identical to female Garganey? Is this
pattern of head striping generic to female 'Anas' ducks?"

I think all female _Anas_ (the genus of most of our dabbling ducks) have
the same basic head pattern, the variation just being the intensity and
number of dark stripes (including whether the crown is dark or not), and
there is probably a little more varation than all of us would like.
Nevertheless, as their bodies are so similar, we're left with head pattern
(and bill color and shape) as a most important field mark. Wigeons are the
most divergent in head shape and pattern among members of the genus.

Although Green-winged Teal usually has a prominent cheek stripe, a good
field mark vis-a-vis Blue-winged and Cinnamon teals, it is variable and, at
its strongest development, does approach the situation in Garganey. I think
female Garganeys always have paler stripes above and below the dark eye
stripe compared with Green-winged Teals, but I suppose there might be
overlap. I just looked at a long series of female Green-winged Teal (Slater
Museum outreach at your service), and in all of them the pale stripes above
and below the dark eyestripe are heavily marked with fine streaks; in
Garganey these areas are usually unmarked (but are they always?
unfortunately, there are no Garganeys available in any local museum for
comparison). The throat is usually contrasty white in female (but not
juvenile) Garganeys, marked with dusky in Green-winged Teals.

In addition, Garganey is a slightly larger, longer-necked (Blue-winged Teal
shaped) bird than Green-winged Teal, but you might need comparison to see
that for sure.

As far as Mallards are concerned, I have the feeling a lot of variation in
Mallards comes from interbreeding with domestic or semidomestic breeds,
including birds that are pale buff all over and birds that have very strong
head stripes. Some of these birds even become feral. Ducks shot by hunters
way out in the boonies have sometimes been odd Mallard breeds.


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