I don't have a whole lot of duck knowledge but from my scant experience I would go by the voices and not the behaviour (I had one female who was a laying/nesting machine but would also be the drake when my drake died and the younglings weren't mature enough).
You clearly have ducks and you know the whisper-quack of a drake vs the shrill LOUD duck one. But it's tough when they're so young they're just whistling.
Side note, dang! You and others have said that pekins are laying machines. I love my scovies and they lay like crazy in the summer as long as they don't have young but... Maybe my Runners were a poor choice (because I can't find the dang eggs half the time!). And I also just realized that (apologies and don't mean to offend) foie gras ducks are a cross between Pekin and Scovy - a runner-scovy cross is less useful. But I've also heard that Pekins don't forage well - that basically they wait by the food area like CornishX chickens do. Meanwhile the scovies and runners "hunt" bugs and frogs all day long.
You clearly have ducks and you know the whisper-quack of a drake vs the shrill LOUD duck one. But it's tough when they're so young they're just whistling.
Side note, dang! You and others have said that pekins are laying machines. I love my scovies and they lay like crazy in the summer as long as they don't have young but... Maybe my Runners were a poor choice (because I can't find the dang eggs half the time!). And I also just realized that (apologies and don't mean to offend) foie gras ducks are a cross between Pekin and Scovy - a runner-scovy cross is less useful. But I've also heard that Pekins don't forage well - that basically they wait by the food area like CornishX chickens do. Meanwhile the scovies and runners "hunt" bugs and frogs all day long.