- Camera takes picture

- Camera pre-checks the picture for quality and that there's something on there that they want

- Camera uploads picture to flock servers

- Camera deletes picture locally

- Rinse and repeat

I could actually see this being done by three jobs in parallel.

If there are a lot of images found on the camera then that's probably because the upload wasn't able to keep up with the amount of data that was created or they have a buffer of a few days or there's a cronjob that deletes these files every now and then...

Unless they actually use the camera also as the storage, which would be really stupid, but sometimes people to stupid things.