I have a downhill in backyard that is full with weed plants and bushes. the total area is around 100ft x 50 ft. the entire area is full with weed and 7 feet tall wild bushes as shown in the picture. There are a 7 tall trees that I want to preserve but would like to get rid of the wild shurbs and replace with some known bushes that would attract birds.

Sorry I'm in zone 4 in US And currently eveyrthing is bare, so it night be hard to identify what the shrubs are.

I would really appreciate any suggestions on how to cut down these wild bushes and what would be a good alternative plants to grow.