In the latest “What If” by xkcd, a reader asks how large a flock of starlings would have to be before gravity began to take hold and forced the group into a huge ball. The answer to the question is really, really large — so large that it would begin to other interesting cosmological effects.
Such a cloud wouldn’t form in the first place without some extra compression. To collapse naturally under its own gravity, the starling cloud would need to be so large that it would engulf the Solar System. When it did collapse, it would heat up, and the starlings…would become a star.
Starlings are know for their massive and complex flocks — or murmarations — which quickly change direction and shape.