Here is what I beleive to be the norm for flying birds and flying insects.
this would be based mostly on my retention
of my readings and I might be way out as I try for flying insects so flying birds may differ lots.
I'm assuming you are using the 1200D and the kit 50-250 with the "IS on" so I would attempt to get the aperture around f8 and be between 1/1000 and 1/2000 and using single point AF (or centre weighted but I tend to get some great backgrounds with a blurry blob in the middle occasionally,WHY CAN"T THEY JUST FLY STRAIGHT?
I try to not go over 800 ISO (but need to sometimes) even in poorer light as I find the insects look grainy or even out of focus and the capture even looks washed out and lacking contrast.
You can squeeze 3 fps out of the 1200D so It would be worth trying to leave it on continuous shooting and hold the button longer for that bonus shot you didn't expect.One other option you may wish to try is "OLD GLASS"
the FD - EOS converter if glassed for infinity focus steals an f stop!
I have a FD 250mm f2.8 that I picked up for $60 (gumtree)
I also have a FD 300mm f4 (borrowed from a kind friend, as good as mine
I picked up a 2x FD teleconverter for $20 (ebay) and that steals an f stop also
That gives you some great bang for buck and the old glass is so much better quality than the newer kit lenses.
the prices are growing with "old glass" thanks to the mirrorless cameras so if you don't like them you can always flog them and make a little profit
Anyhow I reckon you have done a lot more of this than me and been doing it for longer also so I am probably preaching to the converted!
I want to stand as close to the edge as I can without going over. Out on the edge you see all the kinds of things you can't see from the center.