It must have been really dark when you took these pictures since you used ISO 1600 with relatively long exposure times. I was lucky with better light for my shots. To keep my shots sharp I used ISO 400 - 640 and shutter 1/800 s or faster (even 1/1250). It seems I also stood closer to the nest (not far from the pole). I added more shots with 1.4x TC (cheap Tamron) installed on Canon 400mm F5.6L.
http://mareksnis.com/osprey3/index.html
This shot was taken 34 seconds after the previous. The ospreys so a fair bit of circling prior to landing in the nest, probably to check for predators and soaking wet amateur photographers.
