Re: Birds and Gulls...
We've seen too many gulls sitting next to (and even on) those plastic owls, snakes, etc. We hook a wind sock that has lots of streamers onto a fish-hook swivel, then put that at the end of a wire, and one on opposite corners.
The trick is it cannot be fixed -- the entire thing has to swivel, sway, and swoop in the breeze, in addition to the flapping of the pennants. If something is always in the same place or not moving, gulls will soon get used to them.
A neighbor uses a tyvek loon on the same kind of setup. It swoops and soars, never in a predictable pattern.
The other approach is the very thin string or cable or heavy fishline strung back and forth. That seems to discourage them, but it's a PITA to put up and take down. From what I've seen, it's most successful on top of a canopy over a boat lift.