Hi David.
Have you thought of trying Skopelos or Skiathos. They have a great wealth of birds. They don't possess the wetland of Lesbos. But.
Skopelos is mountainous with extensive pine forest (greenest island in Greece). They have the rare birds like Eleonorers Falcon and Adouins Gull.
You can walk down Papadiamantis Street in Skiathos town at night and look up where you can see Eleonoras Falcon using the lights from the streets to catch and feed on the insects flying round. Take a walk through some of the endless pathways on Skopelos and watch Bee Eaters, Blue Rock Thrushes, Hoopoes or walk up some of the mountain tracks and again look up and in the same thermals you can see Ravens, Eagles, Buzzards and Falcons.
These are just some of the fantastic birds you can see on these islands, the list is enormous. I am going to Skopelos in February, I will try and list some that are overwintering there. March/April are the better months for migrating species.
Pan:t: