Fisherman, tourists and especially seagulls turn out in droves in April and early May as the herring “run” from the sea upstream along the rivers of Cape Cod, Massachusetts to lay their eggs. Also called alewives, these swarms of silver fish struggle against the currents and up the “ladders” while birds pluck them out of the water, find a dry rock, swing back their head and gobble them down while neighboring birds squawk in protest.