Mystery Gull in Katwijk aan Zee, The Netherlands

Mysterymeeuw in Katwijk aan Zee

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Ik heb hieronder 2 foto's geplaatst van een eerste-zomer meeuw die aanwezig was in de binnenwatering van Katwijk aan Zee (ZH) op 21 augustus 1999. Dit was een nogal opvallende vogel die opviel door zijn warm lichtbruine tint op schouder- en dekveren met een markante tekening.

   Foto 1   (Jaap Dijkhuizen)

   Foto 2   (Jaap Dijkhuizen)

 

Ik heb eigenlijk geen idee om welke soort het hier gaat.
Voor de goede orde: van de grotere meeuwensoorten zijn gewoon op deze plek: Kleine Mantelmeeuw Larus (fuscus) intermedius en Zilvermeeuw L. argentatus argenteus, gevolgd door Grote Mantelmeeuw L. marinus, Geelpootmeeuw L. michahellis en Kaspische ("Pontische") Meeuw L. cachinnans. De 2 laatstgenoemde zijn overigens vrij zeldzaam. Kijk maar eens goed naar de foto's, want ik zou graag suggesties horen omtrent de (onder-)soort waartoe deze vogel behoort. Op de foto's zijn de meeste kenmerken goed te zien, welke nogal verschilden van de (in grootte gelijke) jonge Zilver- en Kleine Mantelmeeuwen. Vooral de genoemde warm lichtbruine ("buffe") tint op de bovendelen met de zware donkere (bijna zwarte) vlekken maakten de vogel tot een aparte verschijning. Verder waren kop, borst en buik merendeels wit, met wat streping/vlekking op de zijborst. De anaalstreek was grotendeels wit met spaarzame donkerbruine bandering. De staart was wit met een zware, vlekkerige donkere eindband die wit omrand was. Let ook op de rui: de buitenste handpen is oud, terwijl de P8 en P9 nog moeten uitgroeien tot de juiste lengte.
Gaarne uw suggesties!

 

Commentaar is welkom op teus.www@tiscali.nl

 

De binnengekomen suggesties heb ik in een bericht op EuroBirdNet samengevat (19 November 1999). Dit was als volgt:

I received eleven answers to my question as to what (sub-)species birders thought this bird could belong.

Generally, those who responded thought that the choice was between Herring L. argentatus and Yellow-legged Gull L. michahellis. Two thought Lesser Black-backed L. fuscus graelsii was another possibility and even Greater Black-backed was suggested, but then more as a candidate for one of the parents of this bird, thus being a hybrid. The scapular pattern could indeed suggest some Greater Black-backed influence.

But as I stated, most went for argentatus or michahellis. Some were just sure that it was the latter species (see the pictures published in Limicola: Gruber 1995, Klein & Gruber 1997). Most others, however, were cautious and warned for the obvious difficulty that exists when trying to identify birds of this age. Apparently, both species are notoriously variable in this (first-summer/second-winter) plumage, although the knowledge of argentatus appears to be somewhat more extensive under gull watchers than that of (1S/2W) michahellis.

The bird's jizz, although it can be a useful character, was considered right for michahellis by some, but just as right for argentatus by others. Plumage details were hardly mentioned in the discussions, most probably because of the variability in both species.

People from areas where michahellis is common were quite positive that it was this species, although it was acknowledged that a michahellis should show more grey in the upperparts by this time.

Slightly as a surprise to me, Lesser Black-backed Gull L. fuscus graelsii was also mentioned as a candidate (by 2), but others pointed out that this species would show darker and less patterned upperparts. However, a picture that has been published in British Birds (vol. 90, 1997, no. 9, p. 374, pl. 110) depicts a graelsii of similar age that shows a striking similarity to the mystery bird. Although the underparts and the greater coverts are quite darker than those of the mystery bird, the pattern and ground colour of the scapulars and especially tertials are just right. It was stressed by one observer that these rather pale greater coverts generally fit argentatus better than any other of the candidates.

Another birder described ths plumage to be not uncommon under argenteus Herring Gulls. This is sometimes retained throughout the whole of the second winter. They often also produce very colorful bare parts (e.g., brighter pink bill base). Too bad the bird wouldn't stay around to check this!

In conclusion, I cannot but say that the puzzle just hasn't been solved.

Thanks everyone who responded!! And keep on gulling!

 

Teus

 

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