I had a small problem with my camera doing that, so I angled it down just a bit, I think they pick-up heat that is radiating up from the ground and triggers them to take a picture, especially if you have it set to where its over looking a field or large open area, also make sure that its not facing east or west, like RET3006 said, if it faces the sun it will do funny things also.

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GUN-OWNERS, UNITED WE STAND DIVIDED WE FALL.