Rational possibility first: Starlings eat as a colony.
Starlings will chase off desirable fowl.
Starlings are considered pests.
It is possible someone poisoned the colony.
Now for the irrational one: It's the Andromeda strain!
We're all dead!
The MP's infected the birds and were there as crowd control to keep the truth from leaking out!
I think you are on the right track. On a golf course, these starlings munched a fast-working poison as a group, they died as a group. Good riddance.