Lines on rice fields

The rice field I see have rice that look almost ready to harvest. I noticed several days ago, they put lines all across the fields, just above the rice. I'm just curious what purpose that serves, if anyone knows.

Also, there is a patch at one corner of the field that is sort of separated from the rice. It often looks like it just has weeds and has no purpose, but I'm positive there is a reason, just that I don't know what it is. What would that part of the field be for?

Thanks for indulging my curiosity.

I don't know what you exactly mean by "lines," but can that be the shiny tapes they run around/across the rice fields/patches to keep wild birds from eating the rice?

It looks like rope.

Oh, I took a closer look at it and it does look like shiny string, so that must be it. I didn't realize birds would keep away from it. Interesting.