Spring male Northern Wheatears

With reports nationally of an early passage of Greenland Wheatears (Ssp. leucorhoa), I was interested to see if any of the Northern Wheatears passing through Staines Moor over the last couple of weeks could be assigned to this race based on field observations. In his article, Greenland Wheatears (Birdwatch 214: 26-27), Peter Clement points to several features that help separate leucorhoa from the nominate oenanthe in the field: larger size (up to 20%), richer orange-buff underparts extending onto the belly and down the flanks (not restricted to the throat and breast like oenanthe), a broader black tail band, longer wings (by up to 9 mm) and, on males, deeper blue-grey upperparts. However, with variation within our own birds and Icelandic birds showing an intermediate morphology, surely positive identification of birds bound for Greenland would be difficult if not impossible in the field?

At the moor the majority of male birds seen in the last two weeks have showed characteristcs associated with Greenland Wheatear. However, there was a fair bit of variation, and often the structure, posture and colour of a particular bird has appeared to change slightly depending on the light conditions and behaviour.

Click to enlarge

Figs 1 & 2 show fairly classic looking oenanthe birds - a slight, fairly compact structure with the orange-buff largely confined to the throat and upper breast and the rest of the underparts whitish. Note that the bird in fig 2 has a more clearly defined mask and supercilium, appears bulkier due to its posture and is whiter below. In comparison the birds in figs 4 & 5 show a heavier structure, richer orange-buff extending throughout the underparts and perhaps a clearer and bolder black mask and white supercilium. Fig 5 shows the same bird as fig 3 in flight - note the broad black tail band that's over a third, and almost half the length of the tail. Martin Garner suggests an interesting supporting feature for Greenland birds, where their longer wings show between 7-8 primary tips on the closed wing, compared to 6-7 on the nominate race. The bird in fig 6 clearly shows 7 primary tips (click to enlarge), which I guess could place it either camp, but doesn't rule out Greenland. To my eyes, the blue-grey on the upperparts looks pretty much the same on all these birds.

I suspect the identification of actual Greenland Wheatears can only be confirmed with biometrics, but we can at least say a bird 'shows characteristcs of' a bird from Greenland, Iceland or Fenno-Scandinavia, and it was certainly good fun trying to work it out!

More on Greenland Wheatears here:
http://www.birdwatch.co.uk/categories/articleitem.asp?item=692
http://birdingfrontiers.com/2011/04/09/greenland-wheatears/
http://steveblain.blogspot.com/2011/04/leucorhoa.html
http://peteralfreybirdingnotebook.blogspot.com/2011/04/northern-northern-wheatears.html