if i throw pieces of bread onto my yard to feed the birds and a bird drops a piece onto my neighbors lawn and gets eaten by their dog making it

Probably not the first time, becauwe it would probably not be considered reasonably foreseeable that a bird would pick up something on your property, drop it on her property, and her dog woudl eat it and become sick.  However, now that it has happened once, it might well be considered reasonably foreseeable, and you could (emphasize COULD) potentially be deemed negligent and responsible for any damages suffered by your neighbor (i.e. veterinary bills).