Arnhem AEB413

18 October 2014, Meijendel, Wassenaar, the Netherlands

© 2018 by Vincent van der Spek

Redstart headaches: moult & primary spacing

February 25, 2018

Eastern Black Redstart, 1 cy male, October 2008, Kazakhstan (Arend Wassink) 

 

Redstart articles coming up!

The ID article on Eastern Black Redstart vs. hybrids that I wrote with Nicolas Martinez (check his site for interesting info on redstarts and other stuff) for Dutch Birding is still on the desk of the editors. EDIT June 2018: it has now been published

 

Nicolas, Bernd Nicolai and myself (as the 3rd author) also wrote an article on hybrids in Europe from a biological/ ecological perspective that will be offered to British Birds. Once published, I hope to add the pdf to the status and distribution section of this site.

 

Eastern Black in Holland: losing count?

In the mean time the number of Eastern Black Redstart records in the Netherlands is exploding. Two years ago we only had three accepted records: one from 2003 and two from 2012. Since I already shared our ID findings with the Dutch rarity committee CDNA, this bird from 2011 has now been accepted as the retrospective second record (it was rejected at the time since the wing formula was not photographed).

 

The Autumn of the Sibes in 2016 brought no less then three birds, with another one discovered early 2017. And that excludes this bird that was unfortunately not photographed well enough to safely exclude a hybrid Common x Black. 

 

I was lucky enough to find this bird myself on Terschelling, on 5 November 2016, the 6th record:

And then came 2017/2018. No influx in Europe, but nonetheless: there were another two records in autumn and a lovely wintering bird was found in Groningen early 2018. As far as I know no other European country got so many this season! I went out to twitch the Groningen bird:

We now suddenly have 11 records: from mega to 'just' a rarity within a year-and-a-half!

2003: 1

2011: 1

2012: 2

2016: 3

2017: 3

2018: 1

 

How many individuals?

Some birders wondered whether the autumn 2017 records belonged to the same individual, since the bird on Texel popped up the day after the one from Dongeradeel was last seen. 

 

Well, they are different individuals. They e.g. differ in the number of moulted greater coverts, primary spacing and shape and size of the breast patch. See the difference in adult (greyish edges) greater coverts at  Dongeradeel (left) and Texel (right; pics stolen without permission from waarneming.nl from Martijn Bot and Eric Menkveld)

Moult and primary spacing

All Dutch records are of immature males (9 out of 11 birds photographed well enough; the other two seem to show juvenile greater coverts, but a moult contrast cannot be seen; the Maasvlakte bird does how ever show a  contrast between the moulted lesser and median coverts and the seemingly unmoulted greater). 

 The primary spacing and moulted greater coverts of

'my' bird on Terschelling, November 2016

 

I've counted the number of moulted greater coverts and “measured” the primary spacing of these nine birds. In the latter feature, the ratio between the distance of p5-6 vs. p6-P7 is measured (see pic below). This is roughly 1:2 in Eastern and 1:1,3 in hybrids. Since Laurens Steijn's article (2005) this was considered the feature to exclude hybrids from vagrant Eastern, but please note that he mentioned there's overlap, a fact that many have either overlooked, or forgotten! It's not only about averages, the distribution also counts. Measurements given in Steijn (2005): 

 

Hybrid 1 : 1,33 (1 : 1,094 - 2,14)

Eastern 1: 2,19 (1 : 1,57 - 1 : 3,0)

 

The primary spacing of this 1 cy Eastern Black Redstart on Texel, November 2017 is approximately. 1: 1,8 (pic: Diederik Kok):

 

This is not exact science, since the position of the bird has an effect on the measurements, but it gives a rough idea. Please note that the 11th record has not been submitted to the rarity committee yet. All others have been accepted. 

All are way above the average for a hybrid, but basically only the 3rd record is outside their range!

 

Furthermore, please note that all but the 3rd record are actually below the average of phoenicuroides (2,19)according to Steijn (2005) (once more, these measurements should be viewed with some scepticism due to the method used).

 

IMHO this all emphasizes the need for a diagnostic set of plumage criteria. But for the ID (and ecological) stuff you'll have to wait a while longer until we've published! ;-)

 

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