Following the report of a drake Baikal Teal at Marshside RSPB, Lancashire yesterday an image subsequently emerged via social media. The digiscoped image from the finder appeared to show a drake with an unusual face pattern, lacking the black vertical line running from below the eye to the chin.
Initial internet searches failed to find any comparable images of drake Baikal Teal with this vertical line absent, and this aligned with news that a hybrid had been seen the previous week resulted in the incorrect conclusion that this individual was one and the same and of hybrid origin.
Later yesterday evening an image was circulated apparently showing a drake Baikal Teal from Japan that did not show the black vertical line (see here). We did some further digging however and located the original image and additional images taken the same day of this presumed 1st-winter drake in Japan that clearly show it did have the black vertical line albeit a narrow one (see here). In addition communication with the observer of last week's hybrid pointed to a different second individual being involved.
In order to try and clarify the identification and establish whether drake Baikal Teal can ever lack this black line we emailed various individuals for comment. Our first response came this morning from Peter Kennerley, who has extensive experience of Asian duck. Peter made the following comments:
"In my personal experience drake Baikal Teal would always show this vertical line...However it is variable in width, on some narrow, others broad"
"...the lack of a black bar on the face isn't a hybrid character (but could be the result of inbreeding from a captive population?)"
Further comments from ex-BBRC chairman Colin Bradshaw provided a plausible suggestion that may explain the absence of the black line commenting thus
"It not only lacks the dark bridle but also the black triangular patch below the eye that this extends from. What I am not clear is whether the bridle feathers are grown in black tipped white and then the white tip abrades off [quite likely I would think]. In that case this white bridle would be a short-lived but common transient feature of all males. However if they grow in black straight away then it wouldn’t."
After further searching an image taken in Japan in December (see here) and another image of a captive bird here may provide further evidence in support of Colin's comments as both individuals have a faint dark line appearing, perhaps as the paler feather tips abrade.
This all points away from my original thoughts that the facial pattern was as a result of hybrid origin and it will be interesting to see, if this individual lingers, whether the face pattern changes in the coming weeks or the line remains absent. Proving its origin however is a whole different ball game!
A short video from Crossens Marsh was made available (via Youtube) by Pete Hines this evening.