4 sisters---Digging up sunflowers and Corn

Something is DIgging up my sunflower and corn seedling, even sunfloweres that are 8 in tall. I come out to find a stem lying on the ground which appears to be broken off at the root and a small whole. I recently put a 6.5 foot fence around it and I didnt see that it was breached anywhere and zero tracts. I am assuming its birds. best solutions? I have heard CDs, fishing line?

Is there any evidence of digging? or just the plant being cut off at root level? If the latter then it's probably cutworms or voles, voles leave little holes around the place about 1-2inches in diameter. cutworms are much smaller, but if you go out at night you may catch them in the act.

Yes small amount of digging....so whats best way to deter these guys?

Here is some information on voles:

https://permies.com/t/141377/Rid-Voles

Here is about cutworms and slugs:

https://permies.com/t/141380/Young-sunflowers-missing-leaves

I had a similar issue last year. I had to plant my corn 3 times.  I'm not sure, but I think it was squirrels. I put up some dollar store windchimes, tied that silver stuff you use like tissue paper in gifts, it looks like fat tinsel onto bamboo stick, and I sprinkled cyan pepper all over the garden bed.  I don't know what did the trick, but I finally got my corn to grow.  Good luck to you, don't give up.