If you want to freeze action, you need shutter speed. How fast? Well, it depends on the subject. For birds in flight, if you pan along with the subject, you need a shutter speed of 1/1250 second and faster to freeze most wings of larger birds.
How do you get there? Shooting with a wide open aperture gives you a faster shutter speed. Increasing your ISO also increases your shutter speed. In film days, shooting with 50 ISO slide film it was often hard to get a fast enough shutter speed, but with today’s digital sensors able to shoot with minimal noise at high ISO speeds, that is no longer a problem.
For this image, I shot at 1/3200 second and panned along as this great blue heron flew back and forth bringing sticks to its nest. Shooting up into the sky like this, I overexposed one stop to get a little bit of light into the shadowed wings. When shooting RAW like I do, overexposing a little is generally a good idea in most situations, but especially for flight shots like this.
Great blue heron in breeding plumage in flight, carrying nesting material, Joan and Scott Holt Paradise Pond, Port Aransas, Texas, USA. Canon 1D Mark III. 500mm. ISO 800. f/5.6 @ 1/3200 second. EV +1.