Oddly enough, they seem to come in sexually distinct waves. Two females will appear, hop around, snap up some safflower, and then leave. Squirrels, grackles, the blue jay, the finches, they all come through and leave. Then a wave of three or four males will appear. At least one still has some white fluff on him, presumably from fledging, giving him a slightly moldy appearance. They're rather more belligerant to one another. After awhile, they leave, and the females return a few minutes later.
Birds are weird.