You lost me a little there Roy - whilst I agree that manual mode lets you control all the settings yourself rather than relying on the camera selected interpretations, even in full manual mode you are still using the incamera meter to select your settings. In the case of your shutter speed selection, lets assume you have afixed aperture and ISO you want to shoot at - then you use the shutter control and watch the camera meter bar in your viewfinder to then select the right amount for a correct exposure (taking into account any previous experisnces with good metering in the lighting condition your in).
If your in spot pointing at a dark bird in a bright sky your meter will tell you different than if you using a different metering mode.
The whole point of using manual is that you set the aperture, shutter speed and ISO, no matter what metering mode you are in nothing will change unless you manually change it.
What I do is to find the ambient light at my chosen aperture and ISO while in AV mode by metering off something around 18% grey (mid toned grass, grit, grey roof tiles .........). I normally use ISO 400 and f5.6 so if the metering off some thing 18% grey comes up at,say, 1/1000 sec then that is what I set in manual e.g. f5.6, 1/1000 sec and ISO 400.
Now anything that is mid toned in the ambient light will be exposed correctly no matter what the background is. (and no matter what the meter might tell you) no further adjustment is needed. All you do is shoot away.
For dark birds I just click the shutter speed thumb wheel down 2 or 3 notches (+2/3 to +1) in this case to 1/500 sec or 1/640 sec.
For very light birds I click the shutter speed thumb wheel up 3 notches (-1) in this case 1/2000 sec
The actual metering mode I am in is completely irrelevant, yes the metering needle might be wavering around a bit depending on what metering mode you are in but it does not make a jot of difference to the exposure that I have per determined.
I switched to this method almost a year ago and for me it has worked wonders, the number of duff exposures I get now is negligible to what I was getting before - I could never switch back now, I just find it so easy.
That is not to say it suits everyone but most people who try it and master the technique would stay with it that I am sure. Like I said in my first post, getting the exposure right is all that matters and whatever method suits you best is the one you should use.
BTW from what I have read this method is used by most Pro's and serious bird photographers for Birds in flight where birds are likely to fly through varying backgrounds even it they do not use it for perching birds.
P.S. if you use manual and set the exposure to what the metering mode shows then there is no point whatsoever in using manual as you get the same results as you would by using auto.