It has never obstructed my view enough to impair my driving visibility. The act of spraying cleaning fluid on the windshield and using wipers when driving simply smears the droppings across the side of your vehicle. During a sunny day (keep in mind, I'm in Southern California) that smearing can quickly lead to spots and oxidization. When the appropriate moment comes, I pull over to a gas station and clean the windows usually by scrubbing off said droppings and be on my way. Whisking bird droppings away with a wiper just spreads it all over your car. I don't consider myself lazy so scrubbing my windshield by hand isn't very taxing.
Furthermore, if there is too much dust on your windshield and you can't see through it, you either
1. Live in Arizona.
2. Don't do your part to keep your car clean enough for normal operation. And that... That's just sad.
No real mods... just loads of maintenance