bivvying in alpine/winter conditions is not done by choice, by anyone...in the case of alpinists it's because they can't carry a tent and climb at the same time.
unless you are an experienced alpine climber don't take a bivvy to alpine/winter conditions
bivvying in alpine/winter conditions is not done by choice, by anyone.
Well, a considerable amount of alpinists decided to sleep at the top by digging out a snow grave to allow them to put their bivvy in, simply so they can enjoy the night sky and morning sunrise.
Well, no.
People have been successfully sleeping in bivvy during winter, especially on the top of a snow covered mountain.
Having said that, you'd need more gears to stay warm which a tent end up being lighter.