Aside from the technical aspects, which are definitely important, patience and perseverance are vital. Posing for you is no part of any wild creatures agenda so you will most surely spend hours, if not days, in the field with little or nothing to show for it. Frustrating but you'll have earned that great shot which makes it all the more satisfying. And you'll want some good editing skills. Lighting in the natural world is rarely perfect and with fast moving subjects composing is most often done with the crop tool. Most of all just get out there, take pictures and have fun.

Great stuff. I especially like the little Yellow-crowned Night Heron. You might want to take a look at flickr.com. There is a pretty good sizes community of bird photographers over there.

Thanks. That's something to consider.

Thanks everyone who replied to this question. This isn't going to be my livelihood and isn't likely to ever involve any significant amount of money so I probably just won't bother with it.

I always keep the uncropped RAW file so proving ownership wouldn't be a problem.

Thanks. I'll probably just stick a label on the back. We're never going to be talking about huge sums here so I'm not going to loose sleep worrying about it.

I realize this is more of a legal than photographic question but I'm guessing someone in UHH land has dealt with this. I'm toying with the idea of trying to market some of my photographs (hand mounted of blank cards).I want to make it clear that the images are not up for grabs but I'd rather not superimpose writing on the image. Would putting a peel and stick label on the back of the card be sufficient?

I have a 200-500 on a D500 which I carry on a Black rapid sling and shoot primarily birds in flight hand held. I love this lens. It isn't light but I'm 72 and I can shoot all day with it. This is a Peregrine falcon I shot this morning.