I had to have hardware cloth fit into the ends of our gutters to keep the titmice, phoebes and friends out of them. (They have leaf guards over the main sections.) Otherwise they'll try to build nests in there and screw up the downspouts. Mostly the phoebes try to build nests under the deck. We have a cardinal getting ready to build a nest in a bush right outside a window. My wife loves watching them and the hatchlings annually.