Sunday 27 March 2022

A Green winged Teal at Wilstone Reservoir 26th March 2022

Mark (R) and myself decided to meet up at Wilstone Reservoir in Hertfordshire today for a coffee and then go and see a drake Green-winged Teal that Mark had discovered at the reservoir on Thursday.

Wilstone Reservoir is part of a quartet of reservoirs called Tring Reservoirs and whose purpose is to feed the nearby Grand Union Canal. It lies, sort of equidistant, between our respective homes in Bedfordshire and Oxfordshire, so at around 11am we rendezvoused at a local cafe that lies just below the reservoir. After a coffee and chat we then made our way to the only hide on the reservoir to view the  teal. The reservoir, unlike my local Farmoor Reservoir, has reed beds and a large island of trees which makes it much more bird friendly and thankfully there are no water activities, so it is far less disturbed than Farmoor. Consequently and unsurprisingly it has lots more birds.A good number of ducks can be found all over the reservoir as well as nesting Cormorants and Little Egrets on the island, which is all to the good. 

As a bonus, today there were also two Cattle Egrets.

We walked along the grass top of the embankment, such a pleasure after the unforgiving concrete of Farmoor, then turned onto a muddy track winding through the edge of some woodland and which eventually led us to the hide overlooking the water.

Our view from the Hide

We knew the teal was here as someone had reported it earlier this morning and it wasn't long before we picked it up, a little distant, swimming on the water between us and the island. It was in the company of a number of Eurasian Teal, joining them in picking hatching flies from the water's surface.

In fact there was quite a selection here of various commoner ducks such as Tufted Duck,Gadwall, Common Pochard, Wigeon  and Mallard but most notable was a gathering of Shoveler, the majority being drakes, swimming around in a vaguely circular motion, feeding and occasionally displaying to the females.

I confess to being rather partial to a drake Shoveler when seen in its handsome finery. They cannot but fail to catch your eye with their shining white breasts, iridescent bottle green heads and rich chestnut flanks, the colours seeming just that richer when caught in the sunlight.

I returned my attention to the Green winged Teal, watching it swimming and catching flies by endlessly changing direction to snatch the nearest hatching fly, always maintaining a loose and sometimes closer association with its commoner cousins.

There was some speculation amongst other 'locals' in the hide about whether it might be a hybrid. Birders can be like this at times, never really happy unless they can find something to quibble about, albeit benignly.This time it was to do with the border of the speculum which might not have been rusty enough in colour but in the end everyone was happy to accept the duck as genuine. My view was that if it was a true hybrid it would surely show more mixed characteristics than just the very obscure minutiae concerning the border to its speculum.

Let us move on to matters less tedious and of a more general nature!

In essence a drake Green winged Teal looks similar to our more familiar Common Teal.The  defining differences are a very noticeable vertical white bar, on each side of its body, which extends between  breast and flank and no horizontal white scapular line along each of its grey sides. 

Another more subtle difference is the almost complete absence of yellowish buff outlining the iridescent green patch on each side of its head. Also, to my mind the green on its head seemed more luminescent than its commoner congener, especially when caught by the sun.

Although the day was sunny it was hardly warm in the hide as a brisk northeast wind was blowing directly into our faces as we looked out.Once we had our fill of this relatively frequent transatlantic visitor we made our excuses and left.

As with all supposed vagrant ducks the curse of human intervention rears its head.So many ducks from all over the world are kept in captivity due to their attractive plumage, it is impossible to verify the origin of ducks such as this individual. So one has to make a personal judgement for what it is worth and leave it at that. Speculation on this subject can while away hours in hides, pubs and on social media but we are rarely any the wiser.

Green winged Teals were once thought to be conspecific with our Common Teal but are now accepted by all, apart from the American Ornithological Society, as a separate species, based on biological, morphological and molecular differences. 

They are common and widespread in North America and are an annual vagrant to Britain.So many have been recorded here that since 1990, by which time 440 had been accepted  by the BBRC (British Birds Rarities Committee), it is now not considered a notifiable rarity. This bird is the third or fourth to have been recorded in Hertfordshire and is the eleventh that I have personally seen in Britain.

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