When shooting birds of prey, I like to ramp up my shutter speed to over 1/2000, and if the light affords me the luxury, sometimes as high as 1/4000.
While most fast moving animals don’t need to be shot at 1/4000, birds of prey have extremely long wingspans, resulting in incredibly fast moving feathers at the wing tips. Where smaller songbirds can often be shot at around 1/1000, the fast moving outer feathers of a larger winged bird can often come out blurry even at shutter speeds as high as 1/1500. By shooting at 1/2500 or 1/3000, you can often ensure that each individual feather will be suspended in air in a crisp display of the raw power of the bird.
But what about all of the other times when you don’t need to shoot at an incredibly high or low shutter speed? How do you decide what shutter speed to use then? My advice here is to first ask yourself a few questions… Are you shooting on a tripod? Is anything in the frame potentially moving? What is your focal length? These questions will help to make it very clear what a rough starting point may be for a shutter speed. If shooting on a tripod, there is limited potential for camera movement or shake, and thus, a lower shutter speed is just fine, allowing for lower ISO and a sharper aperture.
If you are not shooting on a tripod, you’ll need to decide what’s more important, between higher detail from a low ISO (and therefore lower shutter speed) and thus higher potential for camera shake/blur, and less shake from higher shutter speeds, combated by higher ISO or wider aperture. Typically, in order to keep your exposure the same, moving ISO up means moving shutter speed up.