Cormorants : Mystery Solved!

Trees! They roost in trees! I wouldn't have imagined this of a bird with webbed feet that doesn't really like to fly. There you go!

Cormorants

Every day I take the Thames Path to and from work through the heart of London. Each light morning I watch the cormorants drying their feathers and preening on the various posts in the thames. Yet every night on my way home they have vanished. Where do they sleep?