In about 2003 with my G4 tower I used a great little bit of software called BTV from https://www.bensoftware.com/ It had a motion detection feature which at the time I couldn't find elsewhere.
When my new 'neighbours' moved in recently I looked around the app store for something FREE to do motion triggered recording and didn't find what I was looking for....
The app records video (Image only) in h.264 at the native framerate and size of the source.
It's all in one window with a couple of UI controls.
Drag and Drop the folder where you wish to save the recordings.
Select the input camera source with the button to choose from a cyclic list of all devices found on the system.
It should just start doing it's thing automatically until you quit. It will record clips of 4 seconds or longer if motion is still being sensed.
Adjust the motion sensitivity slider, + for more sensitive, - for less.
The sensitivity slider should compensate for low light levels and small movements such as a light wind in the trees.
I hope it works for you and is reasonably foolproof.
Thanks to howie Bodysoulspirit keithlang et al