Bird droppings vs. powdery mildew?

I have a plant that was under a power line where birds will roost. Over the summer there's been some accumulation. Nothing too bad. I'm getting close to chopping and there are whitish stains on some of the leaves and flowers.

Is there a chance this is bird dropping residue? Or should I be more concerned with powdery mildew. Any way to know for sure?

Thanks!

if its mildew or bud rot, the buds will be mushy, brown / discolored and separate from the plant easily...
i have seen white stains as well - not sure exactly what they are - but im guessing mold would be fuzzy and porous/powdery when handled...

a picture may be good...
hope it helps...

It also helps to know what the birds eat........
If you are lucky enough to have some Pyracantha eating birds, their shit will be red, like the stuff that tears up car paint.
I'm sure you've had to wipe bird bullets off of your car before, so it should be easy to tell the difference between that and the PM.
You'll know right away I think

If the stains look like the one in this vid at 1:55 then it just puddle spots dried up.

http://www.youtube.com/watch?v=NFgwKYKJNaw