First and foremost you have to be a skilled and knowledgeable field naturalist. Hamsa's speciality is birds; identification, biology, ecology and behaviour he is also a licensed bird ringer and has the most amazing eyesight, better than 20/20 if that's possible.
Then you need the technical ability and understanding of cameras, computers, editing and composition he has this too. Like every other sphere of life you also need talent. But give two people the same camera and the same subject to shoot and one will be miles better ta the other because of inherent talent.
On a recent trip to England Hamsa filmed a pair of Atlantic grey seal bulls fighting on a a beach you can see this and some of his other work on Vimeo at: Grey seals fighting
Compare this image of the, "Woods in winter" taken by Hamsa with my effort below. He has whiter, deeper snow, more contrast.......etc.