Now I know what your all thinking; they sleep of course!
But where? Seriously, I live near an inner city beach, and we have seaguls everywhere during the day, but at night they disappear. There’s not many trees around, and the ones that do exist are empty from birds.
During the nesting season, they tend to return to their rookeries. At other times, they find sheltered bays/inlets/ponds and sleep on the water, distant from land predators. I believe that most gulls nest in rocky promontories. (No, I have no idea where gulls along the Florida coast nest–perhaps among dunes.) I have never seen a gull in a tree, unlike herons who are the most unlikely tree-nesters I’ve ever seen.
I have seen them over garbage dumps hundreds of miles inland. they are like rats. If there’s garbage, there’s seagulls.
I have been sailing my boat in rough waters, bouncing all over the place, soaking in the spray, and yet seen the seagulls just sitting there in the water, bobbing up and down with the waves like nothing is happening and looking very comfortable. In the meanwhile my boat is being slammed by waves and I am soaking wet and having a hard time not being tossed around.
I am reminded of the joke:
Q. Why do seagulls fly over they sea?
A. Because if they flew over the bay they’d be bagels. (bay-gulls)
Either Cecil, or one of the Imponderables books deals with sea gulls and parking lots. They prefer flat open areas, in the same way pigeons prefer areas near cliffs. Thus our cities are filled with pigeons and our parking lots with sea gulls.