Great Black-backed Gull

Dark-blue ring with a white four alpha-numeric code, starting letter "V".

note 1 :

Black ring with a white four alpha-numeric code, ending letter ":L (on left tarsus) and metal ring (on right tarsus).

note 1 : used codes are 001:L ~~ 999:L, 000:L

note 2 :

Green ring with a white 2 alpha code (mainly on right tibia).

note 1 : rings are 1,8cm. in height and placed above the knee (on the tibia) for better observation results in the colony (high vegetation) and on rubbish-dumps.

note 2 : the position of the metal ring can be left tibia or left tarsus.

note 3 :

Dark-green ring with a white four alpha-numeric code, starting letter "C:" followed by a colon ":"

note 1 : used codes are : C:1A ~~ C:0A, C:1B ~~ C:0Z. Later change the letter position (C:A1 ~~ C:Z0).

note 2 :

Dark-green ring with a white three alpha-numeric code (number/number/letter) (on one leg) and metal ring (on other leg).

note 1 : used codes are : 01A, 02A ~~ 99Z, 00Z.

note 2 :

Dark-green ring with a white four alpha-numeric code, starting letter "N:" followed by number/number/letter or number/letter/number or letter/number/number (on left tarsus) and metal ring (on right tarsus).   

note 1 : used letters are A, B, C, D, E, G, J, K, L, M, P, R, S, T, U, V, W and Y.

note 2 : not used letters are : F, H, I, N, O, Q, X and Z.

note 3 : used codes are : N:1G1 – N:9G9.

note 4 :

Dark-green ring with a white four alpha-numeric code : (letter (Z) /letter /number or letter / number or letter).

note 1 : first is the letter is 'Z' , code for Galicia.

note 2 :

Yellow ring with a black four alpha-numeric code :
letter / number / number / ":" (colon) / letter "W".

note 1 : used codes are :

Orange ring with a black four alpha code, with as second letter "B".

note 1 : the project runs in Bizkaia, Spain.

note 2 :

Black ring with a white four alpha code, starting letter "G", followed colon ":"

note 1 : the project runs in Gipuzkoa, Spain but also in Bizkaia.

note 2 :