Blyth's reed warbler emarginations and apparent primary inconsistencies

Craig Higson · Status: Offline

RE: Blyth's reed warbler emarginations and apparent primary inconsistencies

Mike Passant · Status: Online

As an old school ringer from the 70s I sympathise with the confusion caused; - please blame the likes of Hartert, Witherby, Ticehurst et alía. I cut my teeth on Svenssons old ringers guide to European passerines (I still have my rather battered orange copy), and so soon felt at home with ascendant (outside in) counting.

As a trainee ringer in 1974, I then struggled to comprehend why passerines in Europe unhelpfully moulted their primaries in descendent order (ie from the 10th outwards);- only Spotted Flycatcher did it ascendently.

As a result of all that, when it came to Gulls I was baffled anew!

All fun though!

Regards,

Mike P.

Ian McKerchar · Status: Offline

To cut a long story short, ascendant numbering of primaries (from the outer primary onwards) is really used by ringers as measurements start from P1, the outer primary, so it makes indicating wing formulae (as with Blyth’s Reed) easier. Not being a ringer myself I’ve never queried it and have always just gone with it and grown to understand which method is used when (ascendant or descendant). Sometimes it’s best not to think too much about it biggrin

colin davies · Status: Offline

John Watson wrote:
I've done a quick Google search on "bird wing topography", and every instance has P1 as inner and P10 as outer - which is logical (as you say)

And yet the the relevant emarginations of Blyth's reed warbler are constantly referred to as P3 and P4 and the Collins guide (amongst others) shows p10 as inner, p1 as outer.

John Watson · Status: Offline

I've done a quick Google search on "bird wing topography", and every instance has P1 as inner and P10 as outer - which is logical (as you say)

colin davies · Status: Offline

I've never been particularly comfortable when it comes to bird topography, I'm never 100% sure if I'm looking at median coverts or greater coverts, but I thought that I had primaries sorted at least. For example the patterns and shape of the mirrors on P9 & P10 can help with gull identification, with P9 & P10 always the outer most primaries.

However the recent Blyth's reed warbler at Hope Carr and the subsequent discussion has really thrown a spanner in the works. When people talk about emarginations on P3 (for example), I (obviously) assume that they are talking about the 3rd innermost primary, yet in actual fact it appears that they are talking about the 3rd outermost.

Every field guide has a page showing bird topography. In the Collins guide it is the very first page of the book. If you look at the open upperwing it shows primary 10 as being the innermost primary adjacent to the secondaries. Yet if you now turn to page 189 of the same book, it shows P10 as being the outer most primary on the painting of Caspian gull. In his book on gull identification, Olson (2003) shows the outer most primary as P10, yet Grant (1982) in his earlier book about gulls shows P10 as the innermost primary. Furthermore, it's not as simple as saying it's a passerine / non passerine difference, because I've also got books which show P10 as the outer most primary for passerines.

So when we talk about emarginations in the 3rd primary, presumably it depends on which system you are using and it would be equally accurate to call it the 7th primary (ignoring the vestigial outermost primary!). Logically (in my opinion) it makes more sense to call the innermost primary P1, since the number of primaries can vary and there is the outer most vestigial primary to add to the confusion.

Can anybody explain the inconsistencies? It's very frustrating when trying to get to grips with a species you're not particularly familiar with. It took me ages last night to work out why I couldn't see emarginations on p3, when in actual fact I was counting from the wrong starting point!

-- Edited by colin davies on Tuesday 22nd of January 2019 08:07:11 AM