I'd guess the berries aren't poisonous to the birds because they've been eating them all summer and none of them have died.
I'm not an expert on pokeweed,,, but read enough about it to know,, that it is poisonous to people. But,,,,, here is the exception. Young plant parts that just sprout in beginning of growing season are eatable by people. There is a certain process to cooking such. Avoid the roots altogether.
It is called Poke Sallet.
The leaves are least toxic, followed by stalks, and berries.
My understanding,,, is; the juice in the berries, is not very toxic. The seeds inside berries are.
When your chickens eat the berries, the seeds go thru the chicken undigested. That may explain why you have had no problems with your flock.
If you eat your chicken's eggs, and do not experience bad symptoms,, then the toxins in the pokeweed seeds, are not absorbed by chickens.
I also think, many other birds will eat those berries. The seeds inside those berries,, also go thru the birds,, and land on the ground far away from plant origin. That may explain how the plant gets seeded all over abundantly.
Here is a link to making/preparing Poke Sallet.
https://www.bbc.com/travel/article/20190318-a-forgotten-food-of-the-american-south
WISHING YOU BEST,,,,,,,,,,,,,,,,,,,,,,,,,and
