Because the Gadwall has few distinguishing marks, it can be a challenge to identify.
Today, as I write these words, it is Veterans Day, and I am reminded of a popular birding term that comes directly from the military. Birders often talk about the giss or jizz of a bird. I have always understood that this birding term stems from the World War II military, particularly Air Force, practice of requiring all pilots to be completely familiar with the General Impression, Size and Shape of all aircraft, so that a pilot (or land-based anti-aircraft gunner) would quickly know whether an approaching plane was friend or foe. Often birders/pilots confronted with a fast flying bird/plane, don’t have the time to consult a bird-book/plane identification manual to properly identify the bird/plane.
Field trip participants are often amazed when either Jewel or I quickly identify a distant flying bird as a Turkey Vulture (top), rather than a Black Vulture or some other raptor. This is not a rare or remarkable skill, as most experienced birders can just as quickly make this distinction because of their familiarity with the jizz of each of these species. Attached is a photo of the two in close proximity so that the difference in the jizz of each is readily apparent. In researching the origin of the terms giss/jizz I found that the history of their usage is much more complicated than I realized. If you are interested see: http://bioacoustics.cse.unsw.edu.au/birding-aus/1995-08/msg00056.html and http://birding.about.com/od/birdingbasics/a/birdingacronyms.htm, and finally: http://en.wikipedia.org/wiki/Jizz_(birding).
On a recent field trip, it became necessary to rely on the jizz of a distant group of ducks to attempt a fairly certain identification of the obvious different species in the group. All of the birds were pretty much just silhouettes in the cloudy daylight compounded by the great distance, right at the edge of the telescope reach to view them. However, we were able to determine that the largest and most numerous of the birds in the group were undoubtedly the expected Mottled Ducks (left), although we surely could not see the bills well enough to determine the sexes of the birds (bright orange - male; olive-orange - female.)
Similarly, the smallest ducks, and second most numerous in the group, were undoubtedly Blue-winged Teal (right), but certainly not presenting as well as the sleep-eyed male in the attached photo. And there were several Northern Shovelers (below, left),which were distinguishable even in the silhouette form by the unique shovel-shaped bill which would be presented to us periodically as the birds shifted and turned from side to side, depicted here in their blah winter plumage. For a series of spring plumage male Shoveler photos, see the bottom row of photos at: http://stlucieaudubon.org/hartBeat/hb2013/hb130310Preening.html.
But the challenge of the day was a pair of medium sized ducks, with flat, blocky type heads, small bills and particularly nondescript coloring. With little more than that jizz to work with, we thought the pair might be the uncommon in Florida, Gadwall. With careful observation the birds occasionally rose and flapped their wings, presenting their whitish underbelly contrasted by the darker gray breast, and the light gray face with a darker cap. Interestingly, the attached photo was taken last November here in Florida.
Shortly after the duck jizz exercise, a very large raptor flew over causing all the birds in the area to take wing. Without the typical white head and tail, we used the jizz of the bird to conclude it was a juvenile Bald Eagle. Then it came close overhead and confirmed our conclusion and presented this photo opportunity.
Giss/jizz is certainly not the “be all and end all” of bird identification. But with practice, it can certainly be helpful to move the ball along on the continuum from “I haven’t a clue what it is …,” to “I think it’s a …,” to “I’m pretty sure it’s a …,” to the final destination of “It’s definitely a …” If you think about it, we use giss/jizz regularly in our daily living, for that is the very technique we use to identify a friend or loved one, too far across a mall parking lot to see their facial features, but familiar enough in their size and shape, and the peculiarities of their gait or mannerisms to know for sure the person is our friend or loved one, and not just some stranger. Of course, sometimes we are wrong, too. Cars, trucks and buses are even easier.