Pugnacious bird fights losing battle against own reflection

I work in thatarea. I can see my rooftop from my office window. Trust me . That seagull is fine because every year at this time they nest and have babies on the roof. The mother and father take turns flying up to the windows and looking at the reflection. Then I watch them go back to the nest. Then they go out to get food. Last year when the chicks were born, as they grew they drank water from the dripping condensation of the rooftop HVAC systems. They had their own little puddles to stay cool in the heat because they couldn't fly yet. And every year, they do the same thing as I and my coworkers have watched them over the years. I think the window ritual must be something they do while protecting the nest.