If it is colder the baby may reject it, or worse, eat it and be unable to digest in a timely manner. Hotter and you may burn the crop. Once the baby is feathered, you want to start offering food. Hawkheads are fruit eaters, so grapes cut in half and apple slices tend to be the first thing consumed. Also make water available at this time, in a shallow container and not too much.
Some babies go overboard and fill their crop with water once they figure out how to drink.
You can offer all kinds of fruit and veggies as well as nutbreads and whole grain breads, pellets and seeds. Hawkheads wean at about 3 to 4 months of age, and they wean slowly. If you run into any problems, at the very first moment you think there might be a problem, run, don't walk, to the avian vet. General Veterinary practitioner often know little to nothing about baby birds. Make sure you go to an Avian vet .