This is what my setup for bird photography soon…
400mm f5,6 L prime lens with Better Beamer flash extender. ‘L‘ is for luxury!
The white lens is a Canon Trademark for long telephoto. Compare with Nikon’s and other brand black lenses.
My setup now, Tamron 70-300mm f4-5.6
The white thing is Tamron 1.4x TC (Teleconverter)