Why do seagulls only sh*t on my window?

I sleep in the Attic that's obviously converted in my bedroom, its a big room, huge roof and the seagulls ONLY **** on my window, I honestly don't know why, do they dislike the glass or something? I look out the window with caution and look along the roof and noticed there is no **** on the roof and thought, wtf are they shitting on my window for? the window is align with the roof, so its diagonal. Im looking at the moment and there is about 5 from 5 different seagulls. Anyone got any comments on their annoying behaviour