This will give you an idea,it was taken on a D7000 using the Sigma 120-400 which didnt have a great reputation,try to get as large a image as you can and keep the ISO below 800 and you will be ok.
The chances of that in the next few weeks would be slim,i can however show you two shots taken one day after the other both from the same position, the bird would have been perched within a couple of feet of the same place each time,the first is the V2 with 55-300 @ 280mm the second is the D7100...
Two of the most popular lenses many start with are the Nikon 55-300 and 70-300 VR versions,they soon find they are too short and often ask can i fit a converter to these lenses,well you can if you shop around enough and find one that will physically fit due to rear elements being too close to...