Terns

species: 
Caspian Tern
scientific name: 
Hydroprogne caspia
notes: 

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

note 1 : used codes are : X00-X99, XA0-XZ9 and X0A-X9Z.

note 2 : that X00-X99 birds are ringed in Germany, while XA0-XZ9 birds are ringed in Poland. X0A-X9Z are not in use yet. 

note 3 : 

website sighting submit: 
Polish Ringing Station
email sighting submit: 
colour-ring type: 
Legring : one, coded.
colour-ring colour (of the c-ring): 
White [W]
colour-ring code (of the c-ring): 
Three alpha-numeric code (3 letters/numbers).
countries where ringed: 
Germany and Poland.
First letter/number (of the c-ring): 
X