My two previous BMW's had issues with bird poop acid etching the paint.. Its is more evident on darker colored paint.
I've learned to always keep a detailer spray bottle in the truck to wipe the bird crap at first sight.
2015 X5 35i Msport, SG, Aluminum Hexagon Trim, Adaptive M Susp, LED Lights, CWP, Ppkg, Driver assistance pkg/plus, 20" M style 469M
2013 X5 35i SG, Cinnamon Brown Leather, Dark Bamboo WT, Conv. Pkg, CWP, MC seats, Running board
2010 535i - Deep Sea Blue w/ NBD Leather, Bamboo Anthracite WT, Sport Auto Trans w/ Paddle shifter, Sports Pkg, PP, CWP, Nav, HD Radio.
2007 525i - Black Sapphire Metallic, Black Nevada Leather, Premium package, CWP, 6MT