Get as close as you can... be focused on the shot you want, not the ones you can get. It's pretty simple, really: just be persistent.
Pic related is 100% crop from
>>3413704 for example. I dismissed the other shots I could have gotten in order to get closer. Either I scared it away taking shots from 100 feet away or got closer by immediately breaking line of sight and climbing for it.
I've been tailing a Barred Owl for weeks trying to get winter shots, and still don't have anything. Sure I could have had a few mediocre shots during that time but was too busy trying to get closer. I don't really see it as a loss because it will be worth it when I do get "the shot".
