Quote Originally Posted by [XC] Oj101 View Post

50/50 by Jonathan Horne, on Flickr

Canon 600D + Tamron 70-300mm f/4-5.6 Di VC USM, 1/320, f/6.3, ISO 100
Need moar ( faster ) shutter speed.
Turn VC off.
Make sure to keep your shutter speed at least 1/effective focal length, which is 1/480s ( focal length @ lens 300mm = 480mm due to 1.6x crop sensor ).
1/480s speed would ensure ( unless you have parkinson's ) that you won't have camera shake caused blur ( shaky hands ).
Then, you'll also need to make your shutter speed good enough to freeze the motion of the birds, that depends on the bird and their flying speed, etc.
Usually 1/640s is good enough to freeze big birds.