A mystery gull, Irakleion harbour, April 4, 2007

This one was much larger than typical "melanocephalus" (Mediterranean) but "small" for "ichthyaetus" (Pallas's). Three pictures (2 of them with zoom in another view) are showed.
This individual came from the east, didn't stay long, did not share the company of the conspesific group, that were feeding and rested just few hundred meters away, but left back to the east soon. Why such a behaviour? Is any possibility of being something else of "melanocephalus"? Is Relict Gull (Larus relictus) a possibility? Colors of bill and legs unlikely to Palla's Gull. Another possibility, a hybrid of melanocephalus x genei has been suspected.
Now, updated this in September 2008, I think of the possibility of an hybrid melanocephalus x ichthyaetus. They are now considered to be close relatives in the same new genus Ichthyaetus.

zoom on air:

The same bird landing:

with a michahellis to compare sizes:

on ground, showing long bill and legs: