Staying alert, being prepared and being at the right place at the right time will certainly bring rewards. I was recently at the Ottawa Nat'l Wildlife Area for the first time of what will be many, I'm sure. One very unexpected surprise was the sight of this first year bald eagle flying overhead. What a gorgeous creature. I was actually concentrating on a black butterfly in the grass that would not sit still for the 300mm lens when I turned and caught this eagle overhead.
Here's another of a red-tailed hawk I caught flying overhead. He showed up and disappeared pretty quickly but I was ready and got this image among a couple others. I had the Nikon D600 loaded with the 300mm f/4 + TC-E14II making for an effective 420mm. Settings were (S) shutter priority 800, ISO 100 with max set to 1600, auto focus set to AF-C and exposure compensation set to +2. It helped knowing my equipment and what it would take to capture birds in flight (BIF) from experimentation and practice, hence, being prepared - meaning I didn't have to fiddle with settings once I slung the camera over my shoulder and set off.
This is a shot of a sandhill crane. I saw a group of four of them in the distance and raised the camera to shoot a series of shots. At first I thought they were great blue herons which I thought was odd because I'd not seen them in groups before. As they got closer I thought they were geese (which made more sense for the group) and was somewhat disappointed because they are so common. Upon viewing them on the computer screen, though, I realized they were sandhill cranes (after looking them up) which are a first for me.