One word of caution - to all about bird crap.
Sometimes it may contain small fragments of rocks - sand etc . . soem birds do consume them to aid digestion - then crap them out.
be careful when wiping off bird crap in the first place - do it with lots of liquid if you want to be sure not to damage the paint. soak it - then dab it up - try not to rub till you have most of it off.
Now, as for your particular problem - Im going to assume you dont have Zaino on the car - .......
Wash the affected area - or the whole car if you want to start over again - with Liquid Dawn Dishwashing soap - the blue stuff. This will remove any wax on the car.
then try the claybar again.
if that fails - try a white vinegar water mix - 50/50 start, and you can go right up to 100 % vinegar if you want. then wash again to remove that.
if stains are not gone - then you have bigger problems and have to consider several options -
ignore it
try to cover it up with a good swirl hiding product
try to remove it with one of the really really fine liquid swirl removers out there - 3M has a series - so do other brands - keep this in mind - abrasives will affect your clearcoat - use with great caution.
go to a pro -
good luck
check out
www.goodspeedmotoring.com for other ideas too