I use a canon 80D and a sigma lens 150-600mm which is a rather long lens.
Actually I started with a more modest 70-300 and it is quite possible to get nice shot with that (it is also a lot lighter and much less expensive... the 150-600mm is still a considered as a budget lens though... can't afford the 12k$ canon lenses right now :) ). A 70-300mm lens if a good way to start.