If the dead birds were Grackles, someone may have sprayed them last night with soapy water. The soap removes the oils from the feathers and the scheduled cold night would kill them.
Better than using poison on the crackling grackles.
Word is that there were three types of dead birds; grackles, sparrows, and pigeons.
Everyone around here thinks Grackles are a nuisance. I think they're pretty cool birds.