Willow Warbler

This photo was taken at the RSPB site at Baron's Haugh, Motherwell during April 2011.
The technical information is as follows.
Camera - Canon EOS 5D Mk II
Shutter speed - 1/1600
Aperture - f11.0
Lens - Canon EF 500mm f4.0 L IS USM plus Canon Extender EF 2x III
Focal Length 1000mm
ISO 800