If you are willing to start hand feeding depends on how old they are. from newborn to 2 weeks of age use a syringe they can have babyfood (humans) or formula for birds that you could find at the local pet store or even online and mix that with warm water freeze in ice cube trays then when ready to start feeding take 1 cube mix with warm water until texture is easily squeezed through the syringe. at 4 weeks or older you can start introducing newer foods like:
Cheerios, sunflower sprouts, pea shoots, millet spray, cooked corn nibblets, cooked carrots *chopped to bite size peices*, hard boiled egg, mashed potatoes with no additives, pellets from pet store you may want to dilute them in a little warm water to soften them if they are close to 4 weeks it may be a little too hard to chew. hope this answer helps!