Friday, 11 March 2011

The real teal? Hmm ...

A record shot of the Connaught Water Green-winged Teal or hybrid (left), with a drake Eurasian Teal (right). On the former, note the 'incomplete' fore-flank stripe, narrow white scapular line, breast colour and head pattern.
There's been a bit of debate about the male Green-winged Teal found last month at Connaught Water, on the edge of Epping Forest, and as it's a true rarity in London I've visited the site a couple of times recently. The identification would probably have been resolved more easily if it swam around on the lake like most ducks and showed properly, instead of behaving like a Woodcock and standing motionless in the leaf litter on a wooded island, usually asleep - which is what it's been doing both times I've looked for it. The island is some distance from the bank, so close observation has been difficult thus far.

An even more distant shot of the same bird (right), with a presumed female Eurasian Teal (left), cropped in to show
the other white vertical fore-flank stripe, which is also a little broken up.
Whatever it is, it certainly has a good quota of Green-winged Teal genes. But whether it's 100 per cent that species is another matter. The vertical white fore-flank stripes are present but arguably not correct, being rather short, not very broad, and 'nibbled away at' by the adjoining grey. Also debatable is the breast colour, which is not as saturated pinky-buff as might be expected.

Like Eurasian Teal, Green-winged has a horizontal black scapular line, formed by black outer webs to the lower scapulars, but it is often less obvious than in Eurasian; importantly, the inner webs of these feathers are brownish-grey and, while they may appear pale, do not contrast boldly with the back, unlike the broader white scapular stripe of Eurasian. In this respect the Connaught Water bird is looking ropey, showing a narrow white margin above the black scapular line which seems no different to how a hybrid would look (for example, compare the images here).

The head pattern can also be debated. There is a distinct pale edge to seemingly much of the green head sides which, though not as clear-cut as on male Eurasian Teal, is apparently more extensive than on typical Green-winged Teal (in the upper photo above it can be seen to run narrowly around the top of the green blaze and down to the bill base, rather than being restricted to the underside). The head colour itself seems very close to Eurasian Teal, not darker brown in tone (a feature mentioned in Sibley but not in the Collins Bird Guide). Check the two shots below to see this difference between more clear-cut individuals of both species, and compare the other features:

Drake Green-winged Teal (Co Clare, Ireland, March 2010). Head colour and pattern, the warmly toned breast and finely vermiculated grey flanks, appearing almost hazy, are useful supporting features to the bold vertical white stripe.
Drake Eurasian Teal (Connaught Water, Greater London, March 2011). The pale border to the brighter brown head is clearly more obvious in Eurasian Teal, though also variable. The grey flanks are much more coarsely patterned.
Taking all features into consideration, my own feeling is that the Connaught Water bird is not pure. It has been said that it probably falls within the range of variation for the species, but whether one bird should show several traits that could be attributed to a hybrid influence is debatable. Until the open wing has been well seen and, preferably, the colour and pattern on the greater coverts analysed from photos, I suspect the debate will run on for a while longer yet; in the meantime, it's not going on my year list.

A closer crop on the record shot of the Connaught Water teal published at the top of this post. The horizontal white scapular stripe is unequivocally white, a feature (albeit more prominently) associated with Eurasian Teal.

3 comments:

  1. Hi Dominic

    While I have not seen many Green-winged Teals and have limited experience I too was almost instantly concerned when I saw this bird. Only 80% of the stripe seems to be solid white and the rest looks to be an illusion caused by paler plumage.

    Along with other things that you mentioned, I did see the open wing. The pattern looked wrong, with the edge of the greater coverts being mainly white or whitish as opposed to the strong rusty colour that I associate with Green-winged Teal. I have mentioned my concerns to a handful of people more well known and knowledgeable than myself and most of them dismissed my thoughts while some agreed. Somebody on site when I was there acquired some images of the wing pattern (which showed what i observed) and may have posted them somewhere on the internet but I have not yet come across them.

    Personally I am going to wait for a classic bird for Green-winged to get on my London list. Even though, as I say, I'm anything but an expert, I cannot see how a hybrid can be confidently elimated here.

    My post on this bird can be found here http://devilbirder.blogspot.com/2011/03/back-to-normal.html

    Kind regards

    David

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  3. UPDATED Thanks for the feedback, David, and interesting to read your blog post. The tips to the greater coverts being mainly whitish would not necessarily be problematic as there is considerable overlap with Eurasian Teal in this respect. However, with that white scapular line I do think this duck is going to find it hard to throw off the hybrid tag. Whether it has come from one of the two local collections or is a wild bird is another debatable point ...

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