Every once in a while in birding, something completely surprises you. Sometimes it’s an assumption that you’ve always had, that you suddenly realize is completely false. Sometimes it’s an epiphany about some field mark – maybe one that every other birder knows, that has somehow slipped past you for all this time.
For me, the Limpkin falls into the category of mistaken assumptions. The first time I saw one, I was amazed at how big it was. I had always just assumed that they were the size of a large rail. So imagine my surprise to discover that the brownish heron standing beside a pond in the Yucatan was a Limpkin.
Female Eurasian Teal and female Green-winged Teal fall into the second category for me. I had always just run under the assumption that they were indistinguishable, and left it at that.
But first a bit of background. Here in western Canada we have three regular species of teal: Green-winged, Blue-winged and Cinnamon. However, a fourth teal, the Eurasian (aka Common Teal), occasionally shows up from breeding grounds in Asia and western Alaska. Several years ago there was increased attention paid to the Green-winged and Eurasian teals as ornithological committees around the world split off Green-winged Teal (Anas carolinensis) from Eurasian Teal (Anas crecca) as two distinct species. There was much rumour and hype that the American Ornithologists’ Union would soon follow suit…they never did. At any rate, whether considered as two separate species as they are in many countries, or as different forms of the same species as here in North America, the stage was set for looking at our teal much more closely.
Fast forward to a birding trip I took to China. We were enjoying scoping out Eurasian Teal flocks in the hopes of turning up new and exotic species. The problem was that due to incessant hunting pressures, these birds rarely stuck around long enough for careful scrutiny. So it was, while watching the tail end of yet another teal flock, that it suddenly hit me what was different about these birds. The upper wing-bar (formed by the greater coverts) of Eurasian Teal is a different colour than on our Green-wingeds. The speculum of Green-winged Teal is bordered by a white trailing edge, and a (variably) buffish upper bar. On Eurasian Teal both of these bars are white. This was good news, for now I could try to pick out a female Eurasian Teal back home in Canada.
Upon coming home and investigating this trait, I found out that it was, in fact, an already published field mark. This and a couple other field marks can be read about here. Now, I don’t think the wing bar difference is 100% reliable. That is, I’ve yet to encounter a Green-winged Teal with a completely white upper wingbar, but some Eurasian do seem to have buffish bars, especially nearer the body. Sibley’s guide states that there is much overlap in this feature, and undoubtedly integradation/hybridization (depending on your taxonomic viewpoint) complicates the matter somewhat. Some birds, as always, are best left unidentified. Nevertheless, this wing bar appears to be one of the main differences in separating the females of these species/subspecies, and knowing this is one more weapon in the birder’s identification arsenal.