Bird droppings are literally the worst thing that can happen to your paint. It can eat thru the clear in a day. Usually it will sink in and crack the clear. Thats where wax comes in, wax can slow down its etching(corrosive process). But it won't stop it. I used to own a BMW that I waxed every month with that off the shelf teflon wax, I think it was made by eagle, after a year and 12 waxes a seagull dropped the bomb on my hood. I told myself this is telfon wax and I wax once a month and its been a year of doing that so lets say at least 10 coats remaining if 2 coats wear away in a year. Well, so I waited a week before washing. Sh**t when I washed it away, my clear was cracked. I felt like suing eagle one. But, I remember now that even if you just took into respect how many waxes I applied in a year, the bird **** still went thru. I have since switched products. I have been using Zaino wax for two years now, and I can tell you that you probably can't find a better and longer lasting shine with any other product, at least that I have ever seen. But, I am sorry I can't test the product to see if it can withstand bird ****, I just wipe immediately when I see bird ****, even if I got to spit into a kleenex and wipe away. I remember that when I drove my BMW for 3 years of that damage I would see it every time I drove as it was towards the driver side window hood. I hope I shed some non scientific light on your problem.
Also, I do need to wax my LR3 since I got it just two weeks ago. I might even take a picture and post it after applying my initial Zaino treatment, but I don't want to blind anyone...