Something in the Ericaceae along the lines of a blueberry. I'm very sceptical that it is an invasive species, unlike the Ivy. The Name That Plant Forum or the NW Forum might be able to help id it more precisely.

floral uk, you are amazing. Standing on your shoulders, I looked up the whole Ericacaea family, and there was a picture of Gaultheria shallon, a shrubby thicket-maker native to the PNW. OP, check here:

https://www.wildflower.org/plants/result.php?id_plant=gash

It's pretty ironic, a native plant overcoming the invasive ivy.

Wow you guys are good. I'd leave the stuff if it wasn't obliterating our juniper hedges. It just grows right through and turns into a bush shading everything out...40% of the hedge is basically gone. Tough stuff, but it looks like birds like it...and we like our birds.

Gaultheria shallon berries are edible and tasty, see https://en.wikipedia.org/wiki/Gaultheria_shallon#Edibility. You are lucky to have so may of them, and without planting and taking care of them.