A very common bird on the beaches of Florida is the Royal Tern, generally roosting just above the waterline. When I went in November there were plenty around, many with fully-grown chicks continually begging for food. Here's a chick with an adult behind it.

I spent a bit of time photographing their antics, but mostly they just loafed rather than doing anything particularly interesting. They're large birds though, large enough that you don't need to use much focal length - I found a bare 500mm lens too much a lot of the time, but unfortunately I don't have anything else. Is it time to repurchase a 300mm f2.8, or could I get away with that new 100-400mm I wonder. I recently cut back on a few lenses, selling three that I have not missed one little bit. You can of course never have the perfect kit bag....