I doubt that the birds are the problem -- more likely, it's low chlorine. Having birds could slightly increase your chlorine demand, but nothing like a couple of sweating middle school boys.

Solution is the same as always:
+ avoid the goop pool stores sell;
+ raise your chlorine with bleach added at in the evening;
+ adjust your pH if it's less than 7 or more than 7.8;
+ test regularly with OTO if you have nothing else;
+ set chlorine levels based on your CYA (stabilizer) levels;
+ get a Taylor K2006 or 2006C so you CAN test higher chlorine levels

Links below; let us know how it goes.

Ben