Baby black

So I found a baby blackbird behind my bin in the back garden. There’s no nest round the back, it’s a north facing garden. Remembering that last Sunday me and my neighbour were talking about the nest in the eves above her bedroom window. 
so I went and put the bird in my cherry tree. 
10 mins later I heard it but it seemed close to my bk garden gate, I went out and my 2 cats had it… so I took it and put it in a box searched what it should feed it. 

3 days 4 nights later im still feeding it soaked mealworms, egg yolk some raisins and water. It knows when I come with the water and opens its beak and if it doesn’t open up I know it doesn’t want a drink. 

im now putting food on my windowsill to try and encourage it to feed itself. I have the window open so it can sit on the ledge. It has no feathers on her belly and her tail feathers are about 10mm. 
when I go out in the garden I take her with me, she’s flapping around building up her strength ready to fly the coop, she’s pooping fine so how long do you think she’s going to be before she is ready to go?