Dipper on The River Tweed

I always struggle to get good sharp Dipper shots as the bird keeps "Dipping " lol also the reflections from the water and the whiteness of the birds breast, just cause me grief, I either end up under exposing the dark plumage, or blow out the white breast.
Any suggestions appreciated.

Brand:	Canon
Camera:	Canon EOS 7D
Lens:	50-500mm
Recording media:	JPEG (digital)
Date Taken:	11 Mar 2012 - 3:32 PM
Focal Length:	500mm
Lens Max Aperture:	f/6.2
Aperture:	f/6.3
Shutter Speed:	1/80sec
Exposure Comp:	+5/3
ISO:	640
Exposure Mode:	Shutter speed priority AE
Metering Mode:	Partial
Flash:	Off, Did not fire

Title:	Dipper on The River Tweed
Username:	borderslass
Uploaded:	11 Mar 2012 - 9:27 PM
Tags:	Dipper (cinclus cinclus), Wildlife / nature
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Votes:	9