Originally Posted by Jhanlon
Have you considered a Canon 100-400mm mark 1? Since the mark 2 came out they're very cheap - I think about £500 or so. I have one and it's agreat (if a little 'soft' compared to the prime and the zoom mark 2). The lens is way more important than the camera and you could get an older 2nd hand body for a couple of hundred quid as I did. I go with Canon over Nikon on ethical grounds (Nikon are overt sponsors of trophy hunting), don't know if that's a consideration for you. Hope this is helpful.
The Canon 100-400 mark 1 (and mark 2) are great lenses. They are pro-level L lenses. The mark 1 weighs 48.2 oz./1,365g without tripod foot. The Nikon 70-300mm VR DX is a pro-sumer level lens and weighs 14.5 oz./412g -- it's a lot of plastic vs metal on the Canon.
You could probably do a Canon 70d or so. I don't shoot Canon, so I cannot really compare it well to the d5500 or similar. It's 20 MP and 7 FPS from 2013. It's probably a great older model camera.
The main difference will be weight. 70d + 100-400 = 2100g. d5500 + 70-300 = 880g.