I used to primarily rely on Canon or Nikon DSLRs for bird and wildlife photography but my health and my age have made both impractical. Thankfully, Micro Four Third (M43) cameras and lenses have improved over the last five years to the point where they have significantly closed the gap with many DSLRs. I now use M43 gear from Olympus as my only camera system.
Olympus and I go way back. I got my first OM series film camera in the mid-1970s. While I started in 35mm with Nikon, I ended up using mostly Minolta and Olympus back in those days. I even carried my gear around in a silver Zero Halliburton camera case. (Those of you who are like me, on the wrong side of 60, will remember those cases fondly, I am sure.) Then, as it is now, the Olympus glass was both spectacular and reasonably affordable and the OM series had the first reliable in-camera light meter. It was a match-needle affair that I thought was the coolest thing ever. That pushed me into the Olympus gear for shooting motor sports.
New Micro Four Thirds Lens Roundup