[Sundae]

The blackbirds are gorging themselves on unripe cherries this year.

I have no idea whether they eat the stones too.
That would certainly make their poo more dangerous. It could crack windscreens.

Also, if I decided that cherry-stuffing would improve their flavour and started to trap them in my garden, would I have to worry about errant stones?

I do not want to crack my teeth.

In truth I suspect I would have to remove the insides anyway, so it is a moot point.
Shot can lodge in any part of the bird, whereas cherry stones will only be found in the digestive system.