Go to your local machine shop. Get iron filings. Mix with starling/grackle bait. Place near the infestation.
Don't expect instant results. The local population will drop, they dead birds won't all be in one place, nor will they drop at onetime. Toxicology tests, should anyone be so motivated, will be negative...
“I’ve seen a horse fly and I’ve seen a house fly but I’ve never seen an elephant fly”