Found a baby bird, what to feed it? Urgent help needed!

Those mealworms were the only worms I saw during my last visit to a pet market.
I will try to find something else, hopefully the soft silkworms.

The bird is still pooping every time I took it out for a ride. Right in my hand too. The color of the poop changes. It used to be greyish with some black in it, later it changed to yellow. It is now back to greyish.