Comparing these two images has made me question again the identification of yesterday's Turkestan Shrike on North Uist.
The top picture is that of a female Brown Shrike photographed in Korea in May, whilst that below is Paul Boyer's image of the Uist bird repeated.
If you click on Paul's image, it will magnify and in doing so, you will find that the very short P2 will equal P6. This fits Brown Shrike rather than Turkestan.
Furthermore, Lars Svensson very kindly emailed me the following today
''Dear Lee,
I trust you saw my quick reply earlier today. The bird is a 99% safe Brown Shrike, not an Isabelline. I have looked again at the two photographs and can add also these three characters pointing the Brown Shrike way: (i) narrow tail-feathers, (ii) not a trace of a pale primary patch near primary-coverts, which a young male Isabelline would show in vast majority of cases, and (iii) extensive and strong scalloping of underparts, which is good for Brown but of course shared by a minority of the most marked Isabelline.
I trust you saw my quick reply earlier today. The bird is a 99% safe Brown Shrike, not an Isabelline. I have looked again at the two photographs and can add also these three characters pointing the Brown Shrike way: (i) narrow tail-feathers, (ii) not a trace of a pale primary patch near primary-coverts, which a young male Isabelline would show in vast majority of cases, and (iii) extensive and strong scalloping of underparts, which is good for Brown but of course shared by a minority of the most marked Isabelline.
But safest Brown Character is that all (at any case longest two) tertials have solidly dark centres with strongly contrasting pale edges. A young Isabelline would have a pattern more like in young Red-backed, with some pale irregular pattern also inside dark subterminal margins. The prominent supercilium in combination with dark 'mask' further supports the identification.
Cheers,
Lars''
1 comments:
A question of wing formula?
Note: in shrikes the outermost primary is vestigial so only nine primaries are readily visible in the field, the outermost visible being P2 (ascendant) or P9 (descendant).
Ascendant numbering is from the outermost primary inwards towards the body; while descendant numbering is from the mid-wing outwards towards the wing-tip.
Ascendant - Descendant
P2 --- P9
P3 --- P8
P4 --- P7
P5 --- P6
P6 --- P5
P7 --- P4
P8 --- P3
P9 --- P2
P10 -- P1
If, as stated, P2 = P6 (ascendant numbering), then according to ‘A Field Guide to the Rare Birds of Britain and Europe’ (Lewington, Alstrom and Colston, 1991) this points towards Brown rather than Isabelline. They give the following data (descendant numbering with P1 being the innermost)…
Brown: Wing formula approx. as in Isabelline, but 9th primary tends to be even shorter (usually = 5th or = 4th/5th, sometimes even = 4th).
Isabelline: The 9th primary = 5th/6th or = 5th.
There are three emarginations, on P8, P7 and P6.
Red-backed: The 9th primary = 7th/6th (sometimes 6th).
There are two emarginations, on P8 and P7.
I would just like to ask for clarification of these wing formulas; are they up-to-date with the latest information for these three shrikes?
Post a Comment