However, size and structure are not good for White-cheeked Tern, and are in fact closer to Common Tern. In this table you can see the biometrics of the mystery tern compared to the Common Terns ringed there yesterday:
It is worth noting that White-cheeked Tern is a scarce summer non-breeding visitor to Eilat, but extremely rare on the Mediterranean coast. During the last 4-5 summers one 'White-cheeked Tern' has oversummered at Ma'agan Michael among the breeding Common Terns (I've seen that bird several times). This bird ringed makes me wonder whether we missed something all of these years.
So, if anyone has interesing info or ideas about this bird, please drop me a line - as a comment here or by email. Thanks!