Babies that have been orphaned for a while will need to be hydrated before being given any food. Gatorade or Lactated Ringers Solution are good hydration fluids. In a pinch you can make your own by boiling one quarter cup water, adding one teaspoon sugar and a pinch of salt. Cool to luke warm, dip your fingers into it and place drops on the top outside of the baby's beak. It will then be able to suck some in, without the danger of aspiration.
Starlings are omnivores but are close to being insectivores.
Parrot hand feeding formula is not an appropriate food for starlings. This is what the normal poop of a nestling starling should look like. It is encased in a coating that makes it easy for the parents to pick up and remove from the nest. A baby that is getting too much fluid, in their food, will have a loose, runny type of poop. Parrots are primarily vegetarians so the nutritional needs are very different for birds that are mostly insectivores.