I've seen a flock of birds fly through a contrail and die immediately. Now either 40+ birds died at the same time for no reason or they were killed by the chems in the trail. Disprove that.
The obvious answer is that although you witnessed the simultaneous death of a flock of birds, you may well have misinterpreted your observations.
Or, you've fallen for the
cum hoc, ergo propter hoc fallacy of logic... (
jroa will like this!)
Many flocks/herds/schools/prides of animals die apparently spontaneously for no obvious causal reason. Whales, fish, dolphins, elks, chickens, cows, even caterpillars and cicadas LOL.
A couple of years ago, thousands of red-winged blackbirds and starlings literally rained from the sky in the US. Necropsies by biologists revealed that the birds had suffered internal injuries that formed deadly blood clots. Thurman Booth, Arkansas' wildlife services director said "There was probably some
physical reason, but I doubt anyone will ever know what it was." No mention of any chemicals in the birds' bloodstreams however.