The lens does have an active mode but I've never used it. I'll give that a try. Why would turning VR off completely help?
Some people argue that the VR system actually
causes blur, especially at high shutter speeds, and/or that at high shutter speeds you should just turn it off as it does at best nothing. I disagree with this, based on my own experience and testing, as does Nikon, Canon, Sigma and probably Tamron (haven't checked their manuals). With modern camera bodies and modern lenses the manufacturer's recommendation is almost always to keep VR on permanently, including at high shutter speeds.
There is something to be said for the
quality of the blur, granted. When VR doesn't work perfectly - typically because you're just pushing it too hard - VR tends to produce more ghosting-like effects where you have multiple sharp edges slightly out of alignment, vs a more smeared, softer look without VR. Some people just prefer the latter, which is fine [as a subjective choice].
But be aware that particularly for small targets, the use of VR can be invaluable if for no other reason than it keeps the viewfinder image more stable and can help you keep the focus point centred on your target. Provided you have camera shake at least mostly under control, you'll then actually more often find that your distant birds are blurry not because of vestigial motion blur, but because the focus just wasn't spot on. Even with VR you'll probably find this occurs more often than you'd like. I recommend deliberately focusing on something else, then go back to the bird and repeat your shot. It simply increases your odds that the camera will focus perfectly. And/or use AF-C mode and just take many exposures while the camera tweaks AF back and forth slightly (this is useful even for close subjects that are furry, feathery, etc, as the AF can't necessarily tell which bit is the eye or the beak or the ear or whatever it is that you're really intending to hit).
Some people say that VR can blur the image if you're trying to pan, but the active mode VR is supposed to take care of that. My wildlife lens doesn't have VR, so I don't have any experience with this.
You have that backwards, at least for Nikon lenses - "Normal" mode is for typical use, where you are stationary but may or may not be panning, while "Active" is intended only for when you are moving (and as such it
doesn't try to detect panning, but rather assumes any such perceived effect is a result of your own motion, and tries to stabilise it anyway). If you don't believe me, check your manual - it'll probably say something like the following, which comes from the AF-S 80-400's:
"Slide the vibration reduction mode switch to
NORMAL for panning shots. When the camera is panned, vibration reduction applies only to motion that is not part of the pan (if the camera is panned horizontally, for ex- ample, vibration reduction will be applied only to vertical shake), making it much easier to pan the camera smoothly in a wide arc."
Backing up to the original topic, I recommend simple persistence for bird of prey photos. If you're out there enough, watching them and being patient, you'll eventually get one fly close by, or even land nearby. I've had a few red-tailed hawks happily sit there on a fence post or in the grass while I walk up to them, all of five feet away, and snap off a hundred photos (I get excited in these situations, as they are rare and precious
).
You'll also just get more familiar with their patterns, habits, hang-outs, etc. These differ by species and geographical location, so it's probably best to just observe for yourself.
