There are many foods that are great sources of nutrition for our wild birds but there are many that can kill them. Blackbirds and other thrushes enjoy fruit in their natural diet. Offering fruit in fall and winter, when fruit is usually not available to them, is a welcomed treat and helps ensure their survival through winter. Apples, pears, grapes and currants are all great sources of nutrition but do not offer citrus fruits. They can be dangerous to wild birds.
Peanuts are a good source of proteins and oils and valuable as a food source for birds.
Whole peanuts, however, can choke young nestlings. In winter you don't need to worry so much about that but in spring it's a good idea to feed them peanut pieces to be on the safe side. Pieces of fat are good as are pieces of bread. There are a few problems that you might encounter when feeding scraps from the kitchen. Uneaten foods are not attractive and can create some unwanted company such as rodents, opposums and cats.