Oh, noise (for the most part, and for any given camera) is inversely proportional to photon count per unit area. Obviously darker areas have more noise than lighter areas, but this isn't really very useful to know as you still need to expose somewhere near correctly. That leaves a single variable as the key factor: ISO. Shutter speed and aperture make no difference at all, only ISO. In this case I was at ISO 400, which is the standard starting ISO for bird work, which you increase as necessary and very seldom decrease. For bird work, shutter speed is your very best friend. Even back in 20D days, 400 ISO was almost as clean as 100, and it is even more so today.
Ideally, for this shot I'd have dropped it to around 200 ISO, but it was a casual shot hand-held from the safari jeep. I was "obviously" too far away for a worthwhile picture .... except that thanks to the magic of the 5DS R, I wasn't!
I get your shutter speeds and distances - a completely different specialty. What gear are you using for it these days? I imagine that the key to getting good results (apart from working well with models, of course) is lighting.
Back to software and noise, DXO's new "Deep prime" processing is brilliant! It takes ages (well, it used to until I discovered that you can set it to use your GPU, which is miles faster than even the current-model i7 in my Thinkpad) but it really delivers the goods. I imagine that the latest versions of other packages are also much improved over the software of, say, 2012. I've been going through my archives and every now and then finding a shot at what used to be an unworkably high ISO which, with PhotoLab 6 and Deep Prime, comes up very well.