Crows is a murder, I think. They'll not affect much, but the cats' presence was probably enough to leave a memory. I don't doubt that as you stock up the garden, adding some attractive trees/shrubs, the birds will come back. At the moment, of course, many are feeding young, or may have done that and are going into moult, so they'll be shy and wary of exposing themselves (excuse the term) and their young to predators. Therefore, it'll be a bit muted for a while. Try sultanas for the blackbirds, and half an apple.
Re the garden, take stock of what's there, and plan it properly. So much better for the time taken.

There have been cats here for as long as we have lived here, any number from 6 down to 2 and back to 4 again. We have birds to spare.
Since the folks before us did not feed the birds it took a while for them to realise that there was food on offer.Keep trying, it only takes one bird to investigate.

Why not start by borrowing a book on gardening in general from the public library?
Cut the grass and weed any paths that need it. If there are flower beds next to the lawn cut the edges of the grass into neat lines. Then you can see where to start, as well as making it look better straight away. If you can identify which plants are weeds start at one end of one bed and remove what you recognise. Anything you can't identify put a photo on here and someone will help. Best not to do any serious reorganising until next spring, when you can see what bulbs are there and which shrubs will flower. If you have any large pots you could put some bedding plants in it (them) and stand them somewhere conspicuous, to cheer yourself along. If there are overgrown shrubs don't prune until you know what they are. Good luck!

Regarding the birds - we moved to our house about five years ago and when we came there were very few birds. I knew there were sparrows down the road, but none in our garden and not much else, though there were overgrown trees and bushes galore!
As soon as the birds came to realise that the two cats were no longer here, they came in droves and we get everything from sparrows with their friendly chatter, wrens (huge song for a little bird), blackbirds, greenfinches, goldfinches, bluetits, great tits, dunnocks, resident moorhens, green & pied woodpeckers, mistle thrushes in the winter as well as the pigeons, doves, jackdaws, crows and the odd sparrowhawk and little owl.
They soon realise that food is on offer and a safe haven. It only took a few months.
It may be daunting with a new overgrown garden, but what fun to find out what will appear and flower next spring!

I too think dont be in a hurry you could well have inherited some lovely plants, bulbs etc. So start with the lawn and identifying any plants so you know when and how to prune etc.
I find with birds they take a while to trust a new contraption but eventually if its safe they will appear also there are times when they just dont visit.

If the previous owners weren't feeding them you are probably just not on their "radar" yet - they'll soon start calling if you keep feeding them!

Hi James! It's definitely shrubs and trees that make all the difference with the birds. When we moved in to our new and barren garden, we never got ANY birds at all! it was desolate...you could 'hear' the silence! now, 7 years on, with a boundary rich in shrubs and trees, we have a garden full of birds. We live very close to a huge....I mean MASSIVE rookery, and there are tons of cats prowling our garden! As for learning to garden.....I learned by getting stuck in, and taking advice from my FIL who was a pro. I was very lucky...sadly he's no longer here. The RHS encyclopaedia of plants and flowers is my gardening 'bible', and Alan Titchmarsh talks such a lot of good common sense too! :))

Many Thanks for all the kind replies
It would seem that the way to learn gardening is to garden
I have started my first project ,which is to convert an old play area into back into fertile ground, and plant some colour. I'm sure I've past the age when it's safe to be swinging a pick axe in this heat but hey go
Thanks again I'm sure to have more questions in the future.
James.