Common Tern

Red ring with a white three alpha code and metal ring (on other leg).

note 1 : starting letter "A", followed by letters. Used codes : AAA-AZZ.

note 2 : birds ringed since 2023.

note 3 :

Red ring with a white two numeric code (00-99) (on left leg) and metal ring (on the right leg).

note 1 :

Black ring with a white three alpha code, starting letter "L".

note 1 : used codes are : LAA-LZZ.

note 2 :

Dark-green ring with a white three alpha numeric code, starting letter "F" (used code : F/number/number) (on left leg) and BTO metal (on right leg).

note 1 : birds ringed in Buckinghamshire, UK.

note 2 :

Yellow ring with black 2 numeric code.

note 1 : birds are marked as pullis at the only colony in Northern Spain, located in the Bay of Santander (Cantabria).

note 2 : used digits are a code of two digits, staring in 00 to 99.

note 3 : 20-30 pulli ringed per year.

note 4 : by end-May some 11 pairs for 29 eggs were spotted.

note 5 :

White ring with a 3 alpha-numeric code (on left tarsus) (to be read from bottom to top) and metal ring (on right tarsus).

note 1 : used codes are : letter/number/number OR letter/letter/number OR letter/number/letter.
NOT used letters are : B, D, G, I, O, U, Y while used letters are : A, C, E, F, H, J, K, L, N, P, S, T, V, X, Z.

note 2 : example of the 3-digit codes : A9A- A9Z, CAA-EZZ or LA1-LZ9 .

since 2016 also letter/letter/number rings have been used, starting letters L and E.

since 2019 E00-E99 have been used in Eemshaven.

in 2021 letter/letter/number rings wil start with A or C.

note 3 : from 2009 on, the middle digit stand for ringing year.
We used C0#, C1#, C2, (used in Limburg) , C4#, C5#. For the Eemshaven: E2#, E5#.

note 4 : some birds -starting letter 'C' are ringed belong the eastern part of the river the Maas in the Netherlands and the used codes are : C2x, C3x (where 'x' is a letter). 

note 5 :

White ring with a three alpha code, starting letter "X".

note 1 :

White ring with a black two alpha code.

note 1 :

Dark-green ring with a black three alpha code (on one leg) and metal ring (on other leg).

note 1 : starting letter "A", followed by two letters.
Used codes are : AAA-AZZ.

note 2 : birds ringed since 2022.

note 3 :

White flag with a black three alpha code.

note 1 : used letters as first letter : A, B, C, E, F ,H , J,K, L, M ,U, V, Y, Z.

note 2 :