A strange Accentor near Rotterdam

12 okt 2014                                                                                                                                                         



10. Accentor spec head 2109200 Rotterdam nl
-maasvlakte the netherlands-








11. Alpine Accentor head: drawing Dementiev, Birds of the USSR.


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On 19th September 2002 on the Maasvlakte in the western part of the Port of Rotterdam I noticed an Alpine Accentor-like bird on top of an Elder Sambucus niger. I only saw it very briefly, at a distance of ca. 10 metres, just long enough to take two pictures fig’s 1 , 2 , 2a . before it disappeared in the dense bushes, I identified it as an Alpine Accentor though arriving at home later that day I had some doubts. When the film arrived some weeks later my doubts were confirmed. Though the first impression: Alpine Accentor Prunella collaris remains, the bird shows some characters which are unusual. 

Most striking are the shape of the bill and the pattern of yellow on it. Vaurie (1965) distinguishes 8 races of Alpine Accentors i.e. Prunella collaris, subalpina, Montana, rufilata, whymperi, nipalensis, tibetana and erythropygia, occupying the mountain ranges between the Pyrenees in Spain in the West to Japan in the East. All races of Alpine Accentor have the same pattern of yellow on the bill i.e. more yellow on the lower mandible than on the upper mandible. The pattern of yellow on the bill of the Rotterdam bird is the reverse, namely more yellow on the upper mandible than on the lower one. See the pictures of juvenile and adult Alpine Accentor taken in Europe fig’s 7-8 .

There are no birds in the collections of Amsterdam, Basel, Copenhagen, Leiden, Moscow or Tring, with a similar bill-pattern as the Rotterdam bird. 

Contrary to what is the norm in collaris the Rotterdam bird has an extensive and solid rufous area on the flanks reaching the sides of the breast. A similar pattern is found in the race rufilata from Turkestan, Keriya range,western Kun Lum. Chinese and Russian Turkestan and which has been described by Vaurie (1965) as ‘Slightly paler than montana but, especially, with the chestnut on the flanks more extensive, reaching to the breast, more uniform, less streaky’.  Rufilata is present in several collections fig’s 12 , 13 , 14 and 18 show specimen from Turkestan in the RMNH in Leiden.  During the third week of September 2002 several long-distance migrants from the same area as rufilata such as Locustella certhiola reached The Netherlands as well. 

The Rotterdam bird is in fresh plumage, it appears to have a dark grey mask which is likely to turn black when it’s plumage gets more worn. A black mask is known from several other accentors such as Prunella montanella, ocularis and atrogularis but not from any of the races of the Alpine Accentor.  

I turned to several collegues and asked them for their opinion. Here is what they had to say: 

Dr. Mikhail Kalyakin of the Zoological Museum of Moscow wrote:’ About the strange Accentor. We discussed it with my colleagues Dr. Eugeny Koblik and Dr. Yaroslav Redkin who have seen Alpine Accentor in the field. We also checked all specimens in our collection and concluded that your picture shows Dunnock: it has common autumn plumage and only one strange thing is an uncommonly straight culmen. But in examination of our collection we have found several birds with the same condition of beak so we think that it is Dunnock without doubt.’

Dr.Jon Fjeldsa, curator of the Zoological Museum of Copenhagen wrote: ‘I can see that it looks odd (especially the bill and eye-ring) but none of our ca. 15 collaris specimens matches it. Two very worn (June) specimens from Nuristan approaches it, though the speckles on the throat are poorly expressed.  So two factors need to be considered: that it is in a very worn plumage and that it could be a hybrid.
However, I don't have sufficient material available and it would be better to ask someone with experience from the collaris range, e.g. in Switzerland or Austria.’
 



12 okt 2014

Dr. Raffael Winkler - Curator of birds Naturhistorisches Museum CH-4001 Basel wrote:’ I cannot help you further.  I  checked my close up pictures of  the heads of Dunnocks that we took at Col de Bretolet  and in most birds there is a slight eyering visible consisting of a single row of white  feathers. I send  you  a picture of the head of one of  these Dunnocks, it is a 1y bird from 11.9.1989 Col de Bretolet fig.9 . If you want you can  also put your questions to a specialist  of  Prunella collaris.’

Dr. Lorenz Heer wrote: ‘Thank you very much for the pictures of the accentor you send me some days ago. It is for sure an alpine accentor Prunella collaris. The yellow at the basis on the bill is just a supporting character, however it is fitting well (the upper mandible is very straight in this individual making this bill very sharp-pointed). However, the most important character are the rufous-brown flanks which are well presented in this bird. Additionally, the undertail-coverts are very typically brown with cream-white edges. Also all proportions are well in concordance with an alpine accentor. Unfortunately, a branch is hiding the greater wing coverts, because they are a very good identification sign for species and age. In this individual, however, the white-black pattern at the throat is not detectable, indicating that it might be an individual which was born in the same spring 2002. This might be the plumage after the first summer moult (while the small pictures included (of a juv.,NDVS) are the first plumage when fledging and before first summer moult), additionally supported by the fact, that the tail feathers (end tips) seem to be worn. For me - having worked with this species for five years for my diploma thesis and PhD - there is no doubt that this bird on the picture is an alpine accentor.’Peter Wilkinson, wrote: ‘Matt Best, Phil Cannings and I had a very interesting session in the British Museum!
I was hoping to be able to write saying that we had positively identifed your accentor, and it was Prunella .........  (or more likely, P.collaris .......). Unfortunately, it didn't quite work out that way. We started by looking through all the accentors in case there was another species that might fit, but, as I am sure you are already certain, there isn't, so we then concentrated on finding a subspecies of Alpine Accentor which shows the red in the position shown by your bird, which is clearly much higher up the breast and sides than in W European birds. This we did find, in some birds labelled nipalensis and from (as one might guess from the name!) Nepal. The specimens were all pretty old, however, and exactly what subspecies that might be called today, I am not sure (BWP doesn't help much with the extralimitals). Thus far, we were encouraged, but after that it became more difficult. Once they are out of the spotty juvenile plumage, all collaris of whatever race show the white flecking on the throat. We did find an October bird with rather reduced flecking, but your bird clearly has none at all and no juv spotting either. The bill also leaves us puzzled: as you say, it is very pointed, quite unlike any collaris in the collection, and had us wondering at one stage whether the bird might be something other than a Prunella (though we can't think what). So, in the end, I am sorry to say that we could not find anything we could confidently identify it as. As it happens, David Snow, retired from the Museum for some years now, was visiting in connection with some HBW work he is doing: we chatted, and I mentioned your bird and showed him the photos - when he heard that we couldn't find a parallel, he wondered if it might be modularis x collaris (we had not got as far as considering hybrid origin, but if that really is a black face mask that is going to become more prominent, as you suggest, perhaps one of the other accentors and collaris ..........?).



I am sorry not to be more help. I guess it must be the only known example of Van Swelm's Accentor (didn't Audubon shoot and then paint two warblers which have never been seen again?)!’

Concluding remarks: It is obvious that the accentor I saw in Rotterdam has not only confused me but others as well. Though most of my friends and collegues recognize Alpine Accentor Prunella collaris  in it, they also see unusual characters as indeed I do, others see Dunnock Prunella modularis see fig’s 3 , 4 , 5 , 6 and 9 .

I found no similar specimen among the Alpine Accentors in the collection of the Natural History Museum in Leiden though the amount of solid chestnut on it’s flanks and breast-sides made it a good candidate for the Turkestan race rufilata. No specimen was found however showing a similar yellow bill-pattern although a drawing in Dementiev (1968) p.755 looks similar fig11 .(yellow colour added by me). If, as has been suggested, the bird is a hybrid, the question as to which species are his parents remains unanswered.

There remains of course the possibility that the bird belongs to a species new to science.Acknowledgements: I like to thank Matt Best, Phill Cannings,  Dr. René Dekker, Dr.Jon Fjeldsĺ,  Hein van Grouw, Szabi Kovács (Aves Foundation), Dr. Lorenz Heer, Dr. Mikhail Kalyakin, Dr. Eugeny Koblik, Dr. Yaroslav Redkin, David Snow , László Szabo (†), Peter Wilkinson, Dr. Raffael Winkler all assisted in one way or another. 

Literature: Dementiev, G.P., and N.A. Gladkov (eds.). 1968. The Birds of the Soviet Union. Vol.VI. Moscow Vaurie, Charles. 1965. The Birds of The Palearctic Fauna. London, H.F.& G. Witherby Ltd. 

Request: If by any chance you recognize the accentor I saw or know someone who does or know where it comes from do not hesitate to contact me: Norman Deans van Swelm, Voorne Bird Observatory, Oostvoorne, The Netherlands.

Norman.vanswelm@wxs.nl 

 

On 19th October 2005 Jacko Holtland videoed through his telescope an accentor near Westkapelle SW Netherlands which shows similarities to the accentor I found on the coast near Rotterdam on 19th September 2002. Although the quality of the images is not great it seems that like my bird his' seems to have a similar yellow bill-pattern, a blackish mask, pale throat, white centre of belly and reddish chest. Please have look and let us know your views.

 

 

 


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