Gulls

species: 
Great Black-backed Gull
scientific name: 
Larus marinus
notes: 

Green ring with a white four alpha-numeric code, first letter 'X'.

note 1 :

email sighting submit: 
colour-ring type: 
Legring : one, coded.
colour-ring colour (of the c-ring): 
Dark Green [G]
colour-ring code (of the c-ring): 
Four alpha-numeric code (4 letters/numbers).
countries where ringed: 
Germany.
First letter/number (of the c-ring): 
X