Common Tern

Blue ring with white 3 alpha-numeric code : letter E followed by 2 numbers (on left leg) and metal ring (on right leg).

note 1 : birds ringed in Berkshire or Tyne & Wear, UK

note 2 :

Orange ring with a black two numeric code.

note 1 : some rings have a dot '.' before the numbers.
 

Orange ring with a black two alpha code.

note 1 : some rings have a bar separating the letters or a dot '.' before the letters.
 

Orange ring with a black two alpha-numeric code (letter/number).

note 1 : some rings have a bar separating letter and number.

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

note 1 : used codes are R01-R99 ; K01-K99,

note 2 : code to be read from bottom till top.

note 3 :

Dark-blue ring with a white three alpha-numeric code (on right leg) and metal ring (on left leg).

note 1 : birds ringed in The Netherlands.
note 2 : used codes are A00-A99 and 00A-99A.

White ring with a black three alpha code (starting letter 'K').

note 1 : project started in 2012, 50 birds ringed so far.

Black ring with a white 3 alpha-numeric code (on left leg) and metal ring (on right leg)

note 1 : birds ringed in the UK, county West Midlands.

note 2 : codes start with A01 - A99, C01 - C99, etc.

note 3 : 

Green ring with white 3 alpha-numeric code (starting letter 'I') (on left tarsus).

note 1 :

White ring with a black 3 alpha-numeric code (starting letter 'I') (on left tibia).

note 1 :