I have seen so many dead birds recently, especially young blackbirds , just lying sprauled out on the pavement or on footpaths. None of them have shown any sign of injury.
I suspect it may be heat exhaustion, so PLEASE all remember to put out fresh drinking and bathing water for them every day and don't let the water get stale because so many bacteria will breed in it in this heat.
Even the baby squirrel who visits us every day has been sprawled out on the fence looking very distressed and has needed long rests between every attempt to climb onto the peanut cage to feed.
wendy, I said this to my hubby last week, that I had never seen sparrows panting like a dog, We have a family of them in our bushes, so they have loads of fresh water now, and I would urge everyone to do the same.
Mind you by all accounts it's to late as you say. :-(