They will eat bread, fat, meat, fish, anything soft. If it is too hard they will soak it in the birdbath. Fun to watch but the crows will scare away smaller birds and even magpies and jackdaws. They are very intelligent. I threw out some gristle and it ended up in the birdbath !
The crows and jackdaws have been here for the past 15 years but only just found my feeder. I absolutely love em so would really like to give them lots of food.
We have a large family of crows living round here, several generations, they never invade the garden feeders or steal food put out for the smaller birds but they watch me when I go out to feed the chickens and I always chuck a bit of wheat out on the field for them and I chuck bread out for them into the field, within SECONDS they flock to pick up the food, always a bit wary but never nasty, very clever birds.