Porcelain Vine: Ampelopsis Brevipedunculata

Are the berries poisonous ?

Yes they eventually turn a very bright blue, pretty but not appetizing. I guess the squirrels eat them.

They must be immune to the poison ,The parks round our new home here are full of squirrels they're so tame they go up to people looking to be fed ...

We have that issue here too at the Parks. Everybody feeds the squirrels so they never have to bury theiir nuts. They literally cozy up to you. All I can think about is the movie "Willard."