The discovery of a female Blue-winged Teal at Daventry Country Park yesterday morning looked set to initiate a local twitch as well as attracting more birders from further afield. Initially located at the south-eastern end of the reservoir it eventually moved toward the dam, where it remained for the rest of the day, favouring the small Lovell’s Bay directly opposite the ranger’s office.
With the arrival of more birders, however, it became apparent that some observers were not entirely convinced that this individual was, in fact, a ‘pure’ Blue-winged Teal. With the bird showing well – at times down to around fifty metres – a feather-by-feather analysis was soon being undertaken as this individual’s parentage was thrown into question.
The feature which cast the most doubt on the birds ‘purity’ was the structure of the bill. It appeared too long and too broad and spatulate for a Blue-winged Teal, recalling that of a Shoveler, a species with which Blue-winged Teal is known to occasionally hybridise.
Suddenly the ‘H’ word was being bandied about and a number of birders formed the opinion that this bird must, therefore, be a Blue-winged Teal x Shoveler hybrid.
This speculation was further fuelled by other features which were believed to be anomalous, i.e. a dull yellowish base to the underside of the lower mandible and, just visible (when blown up) in the photographs above, some yellow/ochre pigmentation at the base of the upper mandible. The legs and feet, too, were thought to be a shade too ‘orangey’ for Blue-winged Teal. Apart from these apparent bare part anomalies, however, there was nothing else radically wrong with the bird.
It appeared to be an adult (juveniles/first-winters have dull, greyish legs) and the thin white border behind the blue coverts, along with the dull green/blackish speculum, indicated it was a female. The remainder of the plumage (loral spot intensity, supercilium and eyestripe extent and prominence) and the dark iris colour were spot-on for Blue-winged Teal, as was the overall cold plumage tone, suggesting an absence of Cinnamon Teal genes in this individual.
I trawled through a number of images on the internet and found some which were good matches for leg colour (it is nowhere near as orange as that of a Shoveler – see the video below for comparison) and it would appear that, according to BWP, the bill colour is not ‘wrong’ for Blue-winged Teal at all. So, is it really a hybrid or is it conceivably a Blue-winged Teal with an abnormally large bill? Did some Shoveler genes get in there somewhere a few generations back? It surely cannot be a first-generation hybrid with so few Shoveler-type characteristics evident. The internet search also revealed a variation in bill size (drake Blue-winged Teals are known to have larger bills than females) although, admittedly, nothing quite as large as the bill on the Daventry bird … Images of a presumed Blue-winged Teal x Shoveler hybrid can be found here while a gallery of pure Blue-winged Teal images can be viewed here. When I was watching the bird in the early evening it was feeding constantly, either alone or with one or two Shovelers. Both the teal and the Shovelers engaged in a ‘hostile pumping’ display when they got too close to each other, i.e. a feeding territorial display (see video), which is said to be common behaviour among ‘blue-winged’ ducks. Despite rumours to the contrary it was fully-winged as is illustrated in the accompanying images.
This very interesting and instructive individual is worth seeing if you get the chance.
It is also worth pointing out that Blue-winged Teal remains a true rarity in Northants with three records comprising an adult drake at Ditchford GP on 13th April 1979, a female or eclipse drake at Thrapston GP from 25th August to 14th September 1985 and an adult drake at Earls Barton GP from 25th February until 1st March 2001.
Many thanks to Bob Bullock and Allan Maybury for supplying the stills used to accompany this post.