How do you remove goose poop from the side of our house?

Bird feces contain caustic substances that can damage surfaces. A good method of removing it from walls is to use a pressure washer, to remove any large particles. Then take a cup of chlorine bleach (laundry bleach) or vinegar (both of these are slightly acidic) and mix this with three quarts of water. Spray this onto the wall, it'll neutralize the caustic. let it sit for about 5 minutes then pressure wash this off. The wall if it is painted may need to be repainted. Clean up any mess afterwards.

*Note: chlorine bleach can injure plants, if you have plants very close to the wall you may want to use vinegar. This 10:1 solution of bleach though shouldn't be strong enough for serious harm.