This gull has a problem. It’s snagged a chunk of protein, probably a mussel, but the good stuff is locked up inside a tough, hard shell. The gull’s jaws don’t have the strength to crush it, and its bill doesn’t have the chisel shape and hardness of the Black Oystercatcher, which would slice this morsel in half in a few strokes. What it needs to do is to fly up about 20-30 feet and drop the shell onto a hard surface. But at the moment there’s so much human traffic on the paved surface above the water that the gull doesn’t want to risk getting its prize — or itself — stepped on by a dim-eyed flatfooted featherless biped. So it takes the shell to water and swims off, waiting for a better time and place.