If your roof or soffit has a crack or gap that birds can exploit, they will use it to get inside your home and build a nest in your attic. Birds will often rip up your attic insulation to make their nest, which can lower the effectiveness of the insulation, leading to temperature dysregulation in the home. Birds may also rip out electrical wiring, which can cause a fire hazard. Birds also love to bring in outside nesting material like dead leaves, dead grass, pine needles, straw and twigs, which can also create a major fire hazard. Birds will also leave behind their droppings, which can contain uric acid, which will damage and corrode buildings over long periods of time. Bird droppings are also known to spread the spores that cause the fungal lung infection histoplasmosis. Birds also carry parasites like bird mites, which they can spread to the rest of the house. Birds inside your attic might also make a lot of noise, which can become a real nuisance while you are trying to sleep.