Not allowed even xmas lights after new years.

Wow! That sucks. That's not very merry ho hoish. I guess that puts my suggestion out of the running.
Perhaps a pet cat would be in order? There is the possibility that your landlords won't allow pets? Or you dislike cats? Hmmmm .... you could get a stuffed animal (like a dog) and put a motion censor in it so it moves and barks when it detects motion. Probably to much work though. Maybe you could buy a kids toy that moves and freaks out the birds?
*Zorbels shrugs* Oh well, I tried. Good luck on your quest to be rid of the pigeons Bilbous, let us know how that works out for ya.