Assuming it’s some subspecies of Eurasian Jay, I’m a bit surprised it’s killing adult birds of any size. Nestlings and eggs, oh definitely, but it’s really not designed for anything larger.

RSPB (in the UK) have it as “Mainly acorns, nuts, seeds and insects, but also eats nestlings of other birds and small mammals.” (going on to mention mice to explain “small mammal”)

Now, the smaller birds know its after their nests, and may have decided to leave, but you might want to check for other causes, e.g. a cat moved in or you’ve entered a season where the birds don’t show themselves (e.g. moulting or just too hot). Also, if the jay is killing the adults, I’d expect a lot of debris left around as they won’t be swallowing them whole.