Based on your description, you're probably getting motion blur (camera shake). 1/60 is pretty slow for a non-stabilized 80-200 telephoto lens. There is a rule in photography that to avoid blur from camera shake, your shutter speed should match the focal length or higher. For example: if you're shooting at 50mm, you'd want at least 1/50 shutter speed; or if you're at 100mm, you'd want at least 1/100.

So applying this to your facts above, 1/60 is a little too slow even fully zoomed out to 80mm. Of course, at 200mm it becomes extremely difficult to get a sharp shot at 1/60, even for a very steady hand.

I'm guessing the reason it changed when you went to auto was because it also adjusted the ISO up. Since you can't go any wider than F/2.8 on the aperture, the only other way to get more light (w/o lowering shutter speed) is to raise the ISO. So, if you were in Aperture Priority mode shooting at F/2.8, what you would do is raise the ISO up in order to get a shutter speed that is at or above the focal length.

Even with the sun up, the camera sees a row of bushes as a pretty dark background. A very nice background for portraits to be sure, but fairly dark. Next time, watch your shutter speeds. If you see them at or below the focal length you're shooting, raise your ISO.