Dabbling Duck Identification in Early Fall


Alexander Henry
 

Hello again,

As mentioned previously, waterfowl migration is picking up with many dabbling ducks beginning to arrive. Actually Green-winged Teal can start to arrive at the Albany Mudflats in early August, but peak numbers of dabblers are not reached until early December, so it is pretty protracted.

One issue with identifying dabbling ducks in fall migration when they are first arriving is that many of the males are in eclipse plumage. So most of the dabbling ducks you will see early on are pretty plain and female-like, which can make things more difficult. It is important to rely on features that are not plumage-dependent, such as size, shape, bill shape and color, leg color, speculum pattern, etc.

I will briefly go over a few of the identifications I think trip people up most often.

GADWALLS. If you see a dabbling duck that looks similar to a female Mallard but has a bright white speculum - its a Gadwall. I think many people overlook Gadwalls and pass them off as female Mallards. There are also subtle differences in head and bill shape. With practice, these differences can become fairly obvious. Gadwalls are generally uncommon at Albany Mudflats in winter - maybe less common than Eurasian Wigeons. But one Gadwall family may have successfully bred in the area this past summer, so you should certainly keep your eye out for them. However at other places like Coyote Hills they can be pretty common.

American Wigeon males molting out of eclipse plumage. I have seen even very experienced, well-respected birders try to identify molting male Americans as hybrid wigeons or Eurasian Wigeons. If the forehead stripe is creamy or yellowish, but everything else looks normal for an American Wigeon, then its an American Wigeon. Some of them look a bit weird right now but give it a couple weeks and they will look more normal. You can even check in on the flock on a regular basis to watch how the molt progresses!

This last one is definitely less important but its a bit of a pet peeve of mine. Identifying Green-winged Teals to subspecies. I do not know how to identify the females to subspecies, and no matter who you are, I don't think you do either. The same goes for the eclipse plumage males - I simply don't think there are any field marks that allow them to be identifiable to subspecies. While it is true that a vast majority of the Green-winged Teal anywhere in the East Bay are always going to be the American subspecies, Albany Mudflats hosted 1 Eurasian Green-winged Teal and 2 intergrades last winter. And that's only the males! So, maybe just leave like 5-10% of them unidentified to subspecies or something like that? Or just wait until the males complete their molt to identify them to subspecies.


Joe Morlan
 

On Fri, 01 Oct 2021 14:58:41 -0700, "Alexander Henry" <awhenry@umich.edu>
wrote:

American Wigeon males molting out of eclipse plumage. I have seen even very experienced, well-respected birders try to identify molting male Americans as hybrid wigeons or Eurasian Wigeons. If the forehead stripe is creamy or yellowish, but everything else looks normal for an American Wigeon, then its an American Wigeon. Some of them look a bit weird right now but give it a couple weeks and they will look more normal. You can even check in on the flock on a regular basis to watch how the molt progresses!
Same thing occurs with Eurasian Wigeon males which molt out of eclipse
quite late in winter. So a bird with the head of a Eurasian Wigeon and a
body of an American Wigeon is far more likely to be a Eurasian Wigeon that
has not completed body molt, than a hybrid. Many times so-called hybrid
wigeon stick around and molt into pure Eurasian males.

Also beware of female Eurasian Wigeons in early fall. They may be eclipse
males.

This last one is definitely less important but its a bit of a pet peeve of mine. Identifying Green-winged Teals to subspecies. I do not know how to identify the females to subspecies, and no matter who you are, I don't think you do either.
Female Common Teal have the wing-bar on the Greater coverts, broader and
whiter than on Green-winged Teal, but there is considerable overlap. There
are some claims of female Common Teal identified in California by a very
broad all white greater covert tips. As for whether these identifications
are correct, I'll quote a former member of the records committee, "What is
truth"?
--
Joseph Morlan, Pacifica, CA


Alexander Henry
 

I seem to remember a molting Wigeon last year in early December which was submitted by someone to eBird as a “young male Eurasian or a hybrid” which I was fortunately able to watch complete its molt and turn into a crisp, clean, classic male American Wigeon.

Regarding identifying eclipse plumage male vs female Eurasian Wigeons, the head color is different. Also, if a bird has the gray feathers starting to molt in on its back, then it’s a male, not a female. Case in point:

On Friday, October 1, 2021, Joe Morlan <jmorlan@...> wrote:
On Fri, 01 Oct 2021 14:58:41 -0700, "Alexander Henry" <awhenry@...>
wrote:

>American Wigeon males molting out of eclipse plumage. I have seen even very experienced, well-respected birders try to identify molting male Americans as hybrid wigeons or Eurasian Wigeons. If the forehead stripe is creamy or yellowish, but everything else looks normal for an American Wigeon, then its an American Wigeon. Some of them look a bit weird right now but give it a couple weeks and they will look more normal. You can even check in on the flock on a regular basis to watch how the molt progresses!

Same thing occurs with Eurasian Wigeon males which molt out of eclipse
quite late in winter.  So a bird with the head of a Eurasian Wigeon and a
body of an American Wigeon is far more likely to be a Eurasian Wigeon that
has not completed body molt, than a hybrid.  Many times so-called hybrid
wigeon stick around and molt into pure Eurasian males.

Also beware of female Eurasian Wigeons in early fall.  They may be eclipse
males. 

>This last one is definitely less important but its a bit of a pet peeve of mine. Identifying Green-winged Teals to subspecies. I do not know how to identify the females to subspecies, and no matter who you are, I don't think you do either.

Female Common Teal have the wing-bar on the Greater coverts, broader and
whiter than on Green-winged Teal, but there is considerable overlap. There
are some claims of female Common Teal identified in California by a very
broad all white greater covert tips. As for whether these identifications
are correct, I'll quote a former member of the records committee, "What is
truth"? 
--
Joseph Morlan, Pacifica, CA


--
Alex Henry


Joe Morlan
 

On Fri, 1 Oct 2021 17:20:38 -0700, Alexander Henry <awhenry@umich.edu>
wrote:

Regarding identifying eclipse plumage male vs female Eurasian Wigeons, the
head color is different. Also, if a bird has the gray feathers starting to
molt in on its back, then it’s a male, not a female. Case in point:
https://ebird.org/checklist/S95381124
Check out this one:

https://fog.ccsf.edu/~jmorlan/euwi.htm
--
Joseph Morlan, Pacifica, CA