How do I stop feathers and excrement coming through my attic bedroom window from pigeons on the roof, while still keeping my window open (it gets hot)?

screen? awning?

Does the window have a screen? If not, you could staple a piece of screening across the window.

If you can, try to put something that prevents pigeons sitting on the roof. We've seen one device on lamposts near trainstations/public areas and its made out of wires. I have no idea what it is called..it looks like wires each standing up vertical, maybe 1 inch tall? Looks like this _l_I_l_l_ These will need to be placed on top of one of our windows outside at our home since birds are pooping on our window too (nest is nearby) perhaps on your edges of the roof.

put an owl statue out there and the potions will stay away

Pigeon pie ... delicious.