You need to stop. J, the pups, and I took off early one morning May with our destination the Pinnacles National Park. Our goal was to see a California Condor on our 6th attempt. We were going to the east entrance of the Park and were driving down Highway 25 went I saw a large bird perched on a snag behind some conifers. I don't know how I saw it but when "large bird" registered I started to stop. A lot of times we keep going, so focused on our end point we forget the journey is just as important. I backed up, got out of the car after grabbing my binoculars, and looked up at the bird. Yes, it was large and as soon as I saw that it was a Golden Eagle I went for my camera. My set up for the day was my D800 with a 300mm f/2.8 lens. By the time I had my camera ready the Eagle took flight and banked right over me looking down. I watched the eagle for at least 5 minutes as she slowly gained altitude and then headed south toward the Pinnacles. We did see a Condor that day although about 1000ft (333m) above us. So remember to stop and from time to time as you travel: you will be rewarded.
Photographing flying birds is very difficult even more so than when they are moving through the tree canopy, through fields, or along a shoreline. The important setting is the shutter speed. When in the field you should try to push up your shutter speed to at least 1/1500s or higher to capture birds in flight. Soaring birds are easier since they are usually at a distance and move relatively slow compared to a warbler taking flight. High shutter speed is required to stop the action.
Your comments are welcomed and if you have any questions about the photo or any other questions leave me a message.