Moerdijk Field Research 2005-2006

(last update: 14 August 2010)

Roland-Jan Buijs
Theo Muusse
Mars Muusse


Age, origin & sex
Retrapped Birds
Upperparts Greytone
Black on Primary Coverts
Black on Primaries
P10 and P9 Patterns
P5 Pattern
Red & Black on Bill
Iris & Orbital Ring
Primary Moult

Larus fuscus graellsii, Moerdijk, the Netherlands.

Valery Buzun, in his 2002 article in British Bird about Heuglin's Gull, describes the underwing pattern of P10 for heuglini. This is white based in most birds. At Moerdijk, we don't see this very much, most of the birds have the base of the underwing of P10 'grey', 'silvery' of 'pale greyish' coloured. Rough estimation would be: white base on the underside of P10 in Russia: 70-75%, for Moerdijk: 1-3%. Again the division line between white and grey is debatable, with all kinds of shades in between (e.g. commonly found in LBBG is a 'silvery grey' base of the underwing of P10, but we consider this still not to be white). Maybe best would be a direct comparison with the pure white greater primary coverts on the underwing, where they meet the base of P10. Some example birds below:

Below: Lesser Black-backed Gull oAZ:

Below: Lesser Black-backed Gull oB4:

Below: Lesser Black-backed Gull mP0:

Below: Lesser Black-backed Gull mV1:

Continue at: MOULT TIMING for heuglini.