I have been a Nikon shooter for over two decades and have recently purchased a Sony Mirrorless System.

I believe that the quality offered by today’s major brands of D-SLR (Nikon, Canon, Sony, Etc) are all more than capable of producing quality images so I would not necessarily promote one brand over another.  Each system has its own pros and cons and I think that photographers should look at a camera system simply as a tool and not be obsessed with pushing one particular brand name.  Find what works for your needs / budget and get out there and shoot with it.

My current primary rig for wildlife photography is a Sony Alpha 7R V Full-frame Mirrorless Camera paired with a Sony FE 200-600mm f/5.6-6.3 G OSS E-Mount Lens.  This rig is also equipped with a Ninja V Video Recorder and Rode VideoMic Pro R Camera-Mount Shotgun Microphone.  This enables me to shoot both 61MP images or 4K 60FPS video.  After shooting photos for decades, I find learning to shoot wildlife video to be a great challenge that keeps me eagerly heading out to the field to discover new opportunities.

My former primary system that I carried in the field for wildlife photography was a 46MP Nikon D850 and a Sigma 150-600mm 5-6.3 Sports DG OS HSM Lens.  Both the body and lens are of metal construction with weather sealing which I consider important features of shooting in the outdoors.  I will also note, this body and lens is a heavy combination weighing in at around 8.5lbs so it may not be right for you.