Warbler waffle: a scoop

First proof that it's the nominate subspecies of Hume's Leaf Warbler that reaches Europe.

Aerobics, the final countdown and warbler taxonomy

Back in the 80s, Hume's Leaf Warbler was still considered a ssp. of Yellow-browed Warbler. Since then not only our hair fashion and taste in music has improved, but also our insights in leaf warbler taxonomy. There are significant genetic, morphological and acoustic differences between the two and acoustic experiments in overlapping breeding ranges show that these species basically ignore each other (Irwin et al 2001). So: different species. No discussion.

But what about Hume's Warbler ssp?

But Hume's Leaf Warbler has two ssp: humei and mandellii. These two ssp. also differ genetically, morphologically and acoustically. Whether you call them species or subspecies, depends a bit on the species concept you prefer (Irwin 2001). The nominate breeds in mountains in the northern part of the Indian Subcontinent, Central Asia, S Russia and Mongolia, while Mandelli's Leaf Warbler has an isolated range in C China, 1500 km away from the nearest breeding Hume's. Hume's winters around the Indian Subcontinent, Mandelli's in SE Asia. Mandelli's is somewhat browner, with a greyer cap, it usually has no upper wingbar and it often has some yellow in the eyebrow and on the underparts (Clement 2017). The genetic distance between the two ssp. is much smaller than between Hume's and Yellow-browed. Hume's and Mandelli's have two song types: a "double note" and something vaguely reminiscent of a squeaky V-belt. The double note slightly differs since it's a bit higher pitched in Mandelli's. Mandelli's als has a higher pitched call. Acoustic experiments however show that Hume's and Mandelli's respond to each other's vocalisations (Irwin et al 2001).

The acoustic experiments are enough reason to regard them as ssp. and as far as I know not a single world list has split them. It's likely that they are in the process of becoming separate species, but are just not there yet.

Figure 2. Genetic variation between Yellow-browed, Hume's Leaf and Mandelli's Leaf Warbler, including the bird ringed in Meijendel.

So what about the vagrants in Europe?

Due to their respective ranges, it's of course the nominate ssp. that most likely shows up in Europe. Both the plumages and calls of Dutch birds I checked also imply that. But I think it has never really been sorted out. So Peter de Knijff analysed some feathers I collected of the bird I trapped on 7 November 2017 in Meijendel, Wassenaar, the Netherlands (the bird on top of this post). The analysis proofs that, as expected, it was indeed a humei. This is the first genetic proof of this subspecies in Europe (Martin Collinson in litt). See figure 2 (made by Peter de Knijff).

No surprises here, but at least we have now established with certainty that humei is the default taxon in Europe.

More details will be published in a Hume's Leaf Warbler overview in Dutch Birding magazine later this year.

Acknowledgements

Martin Collinson confirmed no other humei has been genetically tested in Europe before. Peter de Knijff is once more thanked for his genetic analyses. Peter made figure 2.

References

Irwin, D E , P Alström, U Olsson & Z M Benowitz-Fredericks 2001. Cryptic species in the genus Phylloscopus (Old World leaf warblers). Ibis 143: 233-247

Clement, P 2017. Hume's Leaf-warbler (Phylloscopus humei). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona.

#geneticanalyses #HumesLeafWarbler

Size doesn't matter

Probable Russian Common Gull, 5 February 2012, Meijendel, Wassenaar, the Netherlands

I don't like using measurements as a diagnostic feature to ID sexes or subspecies. Last week was no exception.

After another mild winter, an unusual late cold spell hit the country early March. Temperatures dropped to minus 8 C, combined with a 7 Bft easterly. At the very end of winter... that's just killing. Litterally for the birds if they don't start moving. 

Rinse and I trap four Common Gulls in Meijendel, Zuid-Holland, the Netherlands on 1 March. One large bird is of particular interest since it has a wing length of 398 mm (left) and 399 mm (right).

Based on Malling Olsen & Larsson (2004), Demongin (2016) and Baker (2017) – that together combine many sources – everything above 395mm should be diagnostic for Russian Common Gull heinei. The tarsus (54,2 mm) is well above the average for Common Gull (50,8 mm), all other measurements fit both subspecies well.

But the bird just didn't look right. Or not classic anyway – as far as classic is appropriate for these subspecies. It had a speckled head, and not the desired whitish head with a speckled scarf (reminiscent of a Caspian Gull). The iris was very dark and the bill and legs were dull yellowish to greenish, instead of the prefered plain yellow.

(sorry for the crappy shots; they were made around dawn with my phone)

I also noticed another feature that was completely wrong for Russian: no black band on the 5th primary. 

Though apparently this is not a heinei, based on the much smaller wing lengths of breeding males in e.g. Great Britain (Baker, 2017), I however think it's likely that these large, wintering birds have an eastern origin.

Adriaens & Gibbins (2016) published an impressive Dutch Birding ID issue on the matter:

Just for the fun of it I scored the bird on the 15 features they present. On seven points the bird showed features that the majority of heinei also shows (note that quite a few of these are also majority features for canus), five features are minority features (and these fit canus much better),  and in two it was unclear. The final one - the lack of a black band on p5 - is an absolute no go.  

So apparently it's true: size doesn't matter!

We trapped an apparent canus with with a wing length more associated with heinei.   

The 2012 birds

In 2012 we trapped several likelier heinei candidates (also see pic on top of this post). I didn't photograph the wing well enough to asses all features in Adriaens & Gibbons (2016) properly (how was I to know what exactly to look for at the time!) but out of the 11 features that can be checked, the bird on the photograph scores 10 majority features for Russian. Only the band on the bill could have been clearer. Also note the less intense speckling on the head, the scarf, the medium pale iris and the bright yellow bill and legs.  

And yes, it has a solid black band on p5. The bill length was also in the range of what's considered diagnostic for heinei. 

How was I to know back then that I should have photographed all tongues and black wedges?​ Check the solid W-shaped black band on p5.

After a few birds in 2013 (no heinei candidates), it had been five long years since I trapped some Common Gulls. Let's hope it won't take another five!

References

Adriaens, P. & C. Gibbins. Identification of the Larus canus complex. Dutch Birding 38:1

Baker, J. 2017. Identification of European Non-Passerines. BTO, Thetford.

Demongin, L. 2016. Identification guide to birds in the hand. Beauregard-Vendon.

Malling Olsen, K. & H. Larsson 2004. Gulls of Europe, Asia and North America. Christopher Helm, London

#CommonGull #heinei

Redstart headaches: moult & primary spacing

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! ;-)

#EasternBlackRedstart #CommonRedstart #BlackRedstart #phoenicuroides #hybrids #moult #identification