Hi Charlie - sorry I'm a bit late to this post, still exploring more of the forums.
My thoughts (I've speed-read most of the prior advice - which is very good) and will throw in my 2 pennies fwiw.) Like peter571 I shoot Nikon and am on my second one in twenty years - the first got rain-damaged, expansive lesson learned.
For birds FPS is pretty important as you already know how movement is unpredictable most times.
I agree with the crop sensor comment - adds some versatility and with the newer tech, minimal sacrifice to a non-pro.
There are gobs of tutorials online for both hardware and software. Nikon, Canon, Sony, etc, are all well supported.
Software - I have a long history with Adobe products - started on V.1 and currently use their Photographers subscription (Lightroom/Photoshop.) note: but also agree with spyonabird's pet-peeve on that 😉
While I very rarely use Photoshop on my bird pics, for organization (keywords, rating, sorting, creating collections and quick post-processing I am a Lightroom junkie
What I did was follow a camera that was in my price-range and waited until a newer version came out and the price dropped significantly. The camera I ended up getting was out for over three years when I bought it as a kit (with lens.) Edit: Also look at what lens you may want to use - my recent lens costs almost as much as my camera!
Lastly, maybe look into an Intro to Photography community college class. It will get you into using the camera through regular instruction and assignments. It's also a nice way to network. But again - if you're disciplined, there is a wealth of online instruction/advice.
And, like meghann, there's my ramble of the day - best of luck and stick to your signature; "I get outside...", that's what it's all about!! 🕊️