So what is that, you ask? I'll give you a hint: it's a flock of birds on Lake Superior in August.
Let's zoom in a little.
That is a flock of… loons.
Loons do not flock. Loons are territorial in the extreme. They are completely family-focused. Unless a lake is pretty good-sized, say larger than 500 acres, a pair of loons will take it over and drive off any other loons — or geese or ducks — that are looking for a nice little cottage with picket fence and a place for the kids to play. They will permit their own little feathered progeny hang around the home lake for their first summer but probably no longer.
"Look, guys, a mini shark fin! Oh, wait, that's just Virgil practicing the backstroke.
Virgil, you stop that right now, you here? You almost gave me a heart attack
with your shenanigans. Honestly, the young 'uns these days…"
Loons do, however, migrate. And according to Teh Google, they often form groups, aka, "flocks", to make the long journey south. And that is what we have here.
This site tracks the migrations of loons from two groups, one that nests in central Minnesota, and the other that nests in north central Wisconsin just south of Lake Superior. Certain of the birds have radio transmitters that enable the tracking.