In a gardening class I heard that the berries of the kousa are too large for most of our songbirds. They are edible to humans, but when I ate one, it was not so good! I was told the birds try and eat them, but can not pluck them off the tree because of the size.

Having seen robins pick walnut sized crabs off a tree I doubt if it is the size of the berry that stops the birds.
I had thought they were just bug eaters.

Well, thanks for the feedback. I think I'll probably plant the kousa dogwood because the native alternatives are too prone to disease. I'll just have to see what kind of value it has for birds and wildlife.