Tuesday 7 January 2020

Norfolk ... with some interesting forms ... Grey-bellied Brant ... Alaskan Yellow Wagtail ...

The now renowned dung heap near Sedgeford was still hosting the Alaskan Yellow Wagtail at the end of last week ... despite its name this form, the nominate sub-species of Eastern Yellow Wagtail Motacilla tschutchensis tschutchensis has a breeding range from eastern Kazakhstan to the tip of Far Eastern Russia ...


... this was a strikingly attractive bird ... a male moulting from juvenile into first-winter plumage ... the general appearance was reminiscent of the Blue-headed form of Western Yellow Wagtail Motacilla flava flava except for its dark ear coverts ... also the white supercillium did not extend as far in front of the eye, stopping well short of the bill ...

... it fed for a time around puddles closer to the track than the dung heaps to give close views ...





Not very far away a Grey-bellied Brant was reported in fields near Fring along with several thousand Pink-footed Geese ... this bird proved more tricky than the wagtail ... and the Pinkfeet lifted frequently while some birds came in and out of view in the undulating terrain ... some left the area while others flew in ... and all the while the heavy drizzle piled in on the stiff breeze ...
But then the skies brightened and the Grey-bellied Brant was re-located near Choseley ... and now in much easier terrain ...


... the belly had a distinctly brownish tone as compared with the dark grey belly of Black Brant ... the neck collar was bold, more so than that of Pale-bellied or Dark-bellied Brent Goose ... but did not concentrate to such a dense white area on the ventral aspect as does the neck collar of Black Brant ... rather, the white lines faded towards the ventral surface of the neck ...



... the bird was continually on the move and behaving fairly aggressively towards the nearby Pinkfeet ...
This form has a complicated taxonomic status ... it is not recognised by the IOC ... the latest version IOC 9.2 gives only three sub-species of Brent Goose - Dark-bellied Brent Goose Branta bernicla bernicla , Pale-bellied Brent Goose Branta bernicla hrota and Black Brant Branta bernicla nigricans.

Sebastien Reeber ( Wildfowl of Europe, Asia and North America 2015 ) takes a different and well argued view ... he describes how DNA studies indicate that Grey-bellied Brant have been reproductively isolated from the other forms for 40.000 years in their breeding range in the Western Queen Elizabeth Islands in Arctic Canada ... interestingly the type specimen of Black Brant was taken in New Jersey in 1846 where that form is only an occasional visitor ... the description of that bird seems to be more consistent with Grey-bellied Brant rather than Black Brant.  He cites a paper by Lewis et.al.2013 that gives Grey-bellied Brant the name B.b. nigricans and re-assigns Black Brant as B.b.orientalis  as this is the next oldest available name.
We will doubtless hear more on this ....

At Titchwell roosting Marsh Harriers provide quite a spectacle with upward of ninety birds often present ...


... and also at Titchwell two Spotted Redshanks fed in a deep pool in characteristically frenetic style ...


Along the coast at Wells a Rough-legged Buzzard surveyed the scene from a large bush in the pleasant mid-day sunshine ...



... and a Short-eared Owl flew almost overhead ... 


... a Kestrel hovered similarly close-by ...


... then as the day drew towards its early mid-winter end a walk along the beach at Titchwell seemed to hold little promise in the fading light ... but among a small group of Herring Gulls and Oystercatchers along the shore-line was a smart adult Yellow-legged Gull ...



No comments:

Post a Comment