Young Blackbird - need some advice

Hello Good people,

Have not been on this forum before but need you guys now if you have the time and some expertise.

I think that the small bird that I have is a young blackbird, I became worried when I found one of my dogs had cornered it - when I caught it it looked like it had had all it's tail feathers chewed off (that's what I thought) - but as you will soon be able to tell - I don't know 'jack-err...daw' about birds.
Anyway, it seems that young blackbirds (from what I can find out ) hop around for a while after they leave the nest but can't fly - however, are looked after by thier parents.
Stupid me, I thought it was injured (as it seems to have no tail feathers to speak off & couldn't fly) caught it and kept it in an unused gerbil hutch where I've made a little nest for it and regularly feed it (it asks for food which I place in it's mouth after tickling it under the beak).
I've just read that I should under no circumstances try and look after it???
Also is it normal for them to appear as if they have no tail feathers, will it's mother reject it when I let it go - if that is normal, if not, what should I feeding it, how should I get it ready to cope for itself.

Just to say - the thing that convinced me that I should 'help' it (having read what little I could find - it sounds like I may have done anything but help it) is that I found another one very similar drowned in my pond (with what looked like no tail feathers again - so I assumed that they were getting nipped by the dogs while they were trying to get away!!

Any knowledgable advice would be greatly appreciated.
Thanks
Roger