I think it's just the contrast difference, all the other ones are dark against the reflection of the sky. Lefty is against a dark reflection of the trees so the camera has lit it lighter.
How very prosaic
I think it’s much more likely that the little fellow on the L is drumming his wings a bit and saying ‘lookit this, the world and ‘is !&#@ dog living in %!#@ houseboats now taking up two lanes in our !&#@! river’
(you can see two of the others are looking and nodding in agreement).
btw that lazy curving ’disappearing point’ is brilliant