Alert but nothing on clip

Today I have had a number of alerts on one of my cameras but when I run the clip, nothing moves.
Should only movement within the image clip area trigger the camera or could movement detection outside the area trigger it?

Need to know the camera type to answer with any accuracy.

It’s the Blink Outdoor.

In which case the direct answer to your question is yes, cameras can be triggered by things outside of their visual frame. More so with the XT and XT2, but it still applies to the outdoor.

The reason this can happen is that the initial motion detection has nothing to do with the imaging system. As detailed in the Blink support site, motion detection on this camera is by PIR sensor. The PIR sensor does not perfectly overlay the camera field of view, not by a long way.

For example, you could have a spider, or a fly, walk backwards and forwards over the PIR sensor, multiple times, and it would never even be in front of the lens, yet still it could set off repeated alerts. There are other ways, but hopefully that gives a clear idea of how it could happen.

Brilliant explanation. Thank you for the help, really appreciated.