We only have teeny, shy, elusive and harmless garter snakes here. Currently they are still hibernating & they don’t confront anything but insects.
I tore the place apart, looking for anything. Not a drop of blood. Not a single rat turd. Found a couple more dead chicks wedged behind things.
I looked in every nook and cranny, every container, every bin and found nothing unusual.
Even after a predator attack I’ve never seen birds hiding and dead like that. Hiding yes, but not wedged into tight places and dead.
It does sound neurological like a poisoning and they went hysterical.