1.2 million snow geese at Squaw Creek NWR near Mound City Missouri between February 17 and March 14, 2009. The video contains portions from various days between those dates. I mainly wanted to post this for the long pan of the lake to show just how many were there, since a still image won't do it justice.

extremeinstability.com/09squawcreek.htm

A lot of still images on there including a bunch of Bald Eagles as well.