I am using natural wheat straw right now but notice it gets dirty when it rains so I have to put more on top of it so birds don't eat bird seeds from old wheat straw. What are the best options to use other than natural wheat straw that won't get dirty and get mold? Is pine straw a better option? How do I know if it's safe? Do they put chemicals on pine straw or anything else that can be considered dangerous for birds to eat from? Also if I am using 12 lbs of natural wheat straw, is 100 sq ft of pine straw (30 lbs) the same, less, or more? I know it's heavier but which one will cover more? Does it matter if it's colored or not? I am thinking about buying long leaf one. Is wheat straw safe for birds to walk on like it won't get tangled on their feet or something?