How do I keep blackbirds away from a robin's nest?

The robin has her nest in an evergreen tree on a lower branch by our house. The blackbirds have been sitting in the tree and try to move in closer and also on the roof top of our house. The mother robin has been trying to chase the away. I feel like I am in the movie The Birds in some aspects. There are a lot of blackbirds wanting to get at the nest. How can I protect the robins nest.