A burning question that has raged down through the ages.
Personally, I think they do both. Take our local buzzards.
Normally a solitary creature sometimes seen roadside, more often
gliding overhead at treetop level searching for it’s next meal.
A quite large bird, its presence often is announced by it’s shadow.
Once in a while though, you will see them, and a grand sight it is,
in a large, dispersed flock, of perhaps forty or so, spiraling
on updrafts to heights as I make it of 1500 to 2000 feet.
Strikes me that would be a whole lot of fun.
Islander