The first shot shows the Canon XL-H1 Camcorder with the Canon 500mm F4 attached and shows the distance to the turkeys well. They are just above the red arrow. I used a 17-40mm at 19mm to take this shot. As a side note I did take video with the 500mmF4 attached, both with and without a 1.4 extender. Without the extender, this rig is the 35mm equivalent of a 3,600mm lens, with the extender it is 5,040 mm. This is not as good as it sounds because at those magnifications, mirage (atmospheric disturbances), and vibration from wind become a problem. Still I may get some usable video from this encounter

After an extensive videotaping session, I mounted the 500mm on the 40D and took several shots. Check label below each shot for comparisons.

These are certainly not magazine quality, or as Ronald "Buckwheat" Saffer would say, "Front Cover Shots", but I do think it is amazing what can be obtained at such extreme range.
It is always better to get close if one wants excellent quality photographs, yet this equipment is capable of taking snapshots at amazing ranges if one is unable to approach closer. If conditions are good, the XL-H1 will take usable professional video at these ranges, but one is not able to print high quality enlargements from the captures.
Update
Late in the evening there were more turkeys in the most distant field and now there were several mature gobblers. The birds were milling about and gobbling, preparing to move to a nearby roosting area for the night. This time I used the camcorder with the 100-400mm Canon lens at about 350mm. (for some reason this lens is soft at 400mm when used on the camcorder and does not provide satisfactory high definition video) In this case the turkeys were about 500 yards (1,500 ft.) away. It is always better to get close if one wants excellent quality photographs, yet this equipment is capable of taking snapshots at amazing ranges if one is unable to approach closer. If conditions are good, the XL-H1 will take usable professional video at these ranges, but one is not able to print high quality enlargements from the captures.