Swans

White ring with a black 3 alpha code (on one leg) and metal ring (on other leg).

note 1 : also a 3 alpha-numeric code is used.
Standards used for legrings.
* females always ringed left, males right.
* a white ring means that the age couldn’t be identified, so older than 2 or 3 years. Birds of which the age could be identified, receive a yellow ring (juvenile, birds of the year, 3cy-old birds).
* all birds ringed in Martin Mere start with letter U with an unknown age (so colour white). Birds with a known age (so colour yellow) start with the letter X.
* all birds ringed in Slimbridge start with letter T with an unknown age (so colour white). Birds with know age (so colour yellow) start with the letter Y or Z.
* all birds ringed in Welney, only by Tony Martin, start with letter ‘A’ with an unknown age and with a known age (so colour yellow)  the series 500 are used.
* in the past birds in their breeding territories were ringed with a white ring (unknown age) starting with the letter ‘T’ for adult birds and with the series 300 and 400 for known age birds. Birds ringed during summer 2004 in the Pechora-Delta/Russia have the same combinations as the adult birds (age unknown, so white ring) : 11A-Z, 12A-Z, 13A-Z, 14A-Z, 15A-Z. Birds with a known age received the yellow 400-serie.
* series starting with B, S or E are used long time ago, birds are probably already dead. [it seems that an occasional bird is still alive] E-code were used in Martin-Mere, while S was used in Slimbridge.
* letters like E, G, K, M, O, Q, R and W are not used in end-combinations.