Sorry if I'm not being clear enough.

Regarding About Custom setting Menu a3:
- 51points 3d tracking will follow your subject, it is important to keep the shutter pressed half way.

- 51 points alone, does not track the subject, you can select any of the 51 , but the focus point will not change automatically.

For others reading this, the 3D tracking is available in the D300, D300s, and I guess all higher models. It is not available in the D40, I'm not sure about other Nikon models like the D90

Another variable is the focus vs. shutter priority "Custom setting Menu A1 (AF-C priority)" this allows you to take a photo in the following situations:
- FOCUS priority: Photo is taken until perfect focus is acquired (being it the bird or the background )
- RELEASE+FOCUS Photo is taken even if not in perfect focus, more useful during bursts of photos, speed of the burst maybe slowed down to allow the focus to keep up
- RELEASE: Photo is taken the moment the shutter is pressed . this is default setting.

Now we need to go find a flying bird and try it out. :thumbsup: