I only started bird photography last spring, so I am still pretty green in that field but I discovered a few things. The first one is birds are creature of habits. They do not go with the flow or where the wind will push them. They have a territory. Looking for food takes a lot of their time and most important they have habits that you can discover very easily. For example after two field trips to the river, I noticed that those females Common Merganser reached their feeding area by coming on the river from downstream at around 9:30- 10:00 am. They always used the opposite side of the river from where I was, reached their fishing area and stayed there for about one hour.
I knew that if I wanted a close shot I had to get closer. So on my fourth visit, I walked in knee deep water up to a small island in the middle the river, sat down and waited. 10:00 am, here they were and I was able to get those closer shots. After I was done I noticed 2 photographers on the shore, looking at me green on envy. They knew I was much closer and my shots would probably be much better than theirs.
If you do bird photography, sit and look, learn their habits, do not be afraid to get dirty or wet and this will help you get the best spot for your photos. And be ready to go to the same place a few times before you get the shot you want.