best settings for birds & BIF?

capturing people in action usually requires a shutter speed of about 1/250s if not faster when light is challending ... birds in action would likely require 1/500s or faster ...

i suppose you could look at flickr.com and search for 120-400 to find pictures of birds in flight taken using lenses similar to yours ... when you find a shot of a bird in flight click 'actions' and 'view exif info' and you may see shutter speeds of 1/1250s ...

good luck ...