I have been feeding raw peanuts (in shell) to the squirrels who live in our trees. Blue jays and cardinals like the peanuts too but they have to work much harder to open the shell.
An element of trust has developed in the behavior of the birds and squirrels. They don't run or fly away when I open the door. They sit on the outdoor furniture waiting for the gift. In fact, there are two squirrels who sidle up to me and let me bend down to offer a peanut in my hand. They gently take the peanut in their teeth and scurry away.