Why Birds Flock To Buildings Birds seek areas where they can roost and nest, well-protected from the elements and predators, with easy access to food and water. Many times, these shelters are beneath bridges, on building roofs, cornices, and HVAC units, among other electrical equipment found in substations. Each of these areas can attract hundreds of birds that leave behind both an aesthetic mess (droppings) and highly corrosive uric acid, which is found in their urine.    Da