A roof’s life expectancy can literally be cut in half by nothing more than the steady accumulation of bird droppings. When pigeons, starlings, or sparrows build nests in rain gutters, drains and roof corners become blocked. This results in standing water during rains, water that not only rises enough to seep under roofing tiles but creates pools heavy enough to seriously damage and even collapse a roof. Damage to AC Units

Pigeons and other birds often build nests around and under rooftops of commercial and apartment buildings. They are also not too shy about building nests around coolers and AC units. These structures typically allow just the right amount of room for pest birds like pigeons to nest and roost.

It doesn’t take long for these birds to multiply, for pigeons, like most birds, is drawn by the scent or smell and noise of other pigeons. So it doesn’t take long for dozens of pigeons to nest around and under these units and structures. When this happens, expensive rooftop AC systems will quickly fall victim to feathers, bird droppings, and nesting materials. This debris can clog and damage the vents and propellers of these systems. And that means expensive repairs and or replacement. Damage to Ventilation Systems

Bird nests built in chimneys and around rooftop ventilation systems will block airflow into a building. In Cleveland, USA, a family of five was killed by carbon monoxide poisoning just before Christmas 1995 because their fireplace exhaust system was blocked by bird nests. Damage by Fires

The small twigs, feathers, and dried droppings found in bird nests make excellent kindling for fires. When birds build their nests inside electric machinery, all it takes is a heated bulb or tiny spark to ignite a fire that can destroy an entire building. Many electric sign companies blame bird nests for many of their sign fires.