Do not feed hand-feeding formulas intended for parrots to insectivores. The only passerines "Kaytee" and others will work for are columbiformes, that being pigeons and doves, as they are granivorous and feed on regurgitated foodsolely crop milk for the first weekfrom their parents. Omnivorous passerines such as house sparrows, starlings and robins, require not only a high protein and fat percentage, but food that has substance. They will not and cannot thrive on liquids. Hand-feeding formula is to be mixed until it is the consistency of yogurt or pudding, and this is easily aspirated by the majority of passerines.
To understand how to feed them, one must understand how they are fed in the wild. Their parents do not regurgitate food to them, but merely carry it to them. Full bugs and berries, the former crunched in the beak just enough to be killed before fed to the young, or sometimes broken in pieces and fed to many young, are offered by both parents throughout the day. Every 20-30 minutes when the babies are very young. The berries provide water.
The best a hand-feeder can do is to feed, obviously, the same foods. Earthworms and live worms are not acceptable, but other bugs (so long as they are cut into pieces and not live when fed) are a great source of protein and nutrients. Blueberries and blackberries and sometimes red grapes will not only provide water, but give the diet diversity.
Cat or dog food is an acceptable substitute, but must be supplemented also with grapes and berries, cut into small, bite-sized pieces. They can only be fed in moderation, as the bulk of the diet should be protein.
Passerines need not and should not be fed with a syringe to one side of the mouth. People mistake the feeding methods intended for parrots to be for any bird. They are not. Parrots are fed regurgitated food (and sometimes crop milk, in the case of budgies and a few others) from their parents, who grip their beaks with their own to pass the food between them. With the exception of columbiformes, passerines place the food inside of their babies' mouths.