What Lens are you using on your E-M1 or m4/3 camera for your Bird shots.

I have been trying out my Canon 70-200 f/4 L lens it weighs 765gms and goes well on the E-M1 with the Kipton adapter a great combo except for the manual focus. Dont mind MF close up when shooting with a Macro Lens Insects or Flowers, though I am no good using it with Birds I cannot focus on their eyes fast enough from a distance before they fly off, its ok if they are at the Bird Bath and rest for a while to have a drink, even then I cannot get the focus spot on hand holding.

Been researching the Olympus 50-200mm at 995gms I would have to get an adapter that may be the lens for me.

Thought about the Panasonic 100-300mm 520gms, read don't expect miracles with moving objects ? Birds move

So what does that leave me with the Olympus 75-300mm 423gms, are there any other light weight lenses or different brands out there I have missed.