Rather than straw from cereal grains (like wheat, oats, rye, etc), which have large thin walled stems that collapse and mat down, use coarse GRASS hay instead. Old wasty stuff. Grass hay has a small, strong walled stem and does not mat like straw does. Pile it deep......like 6 to 8 inches to start and add to it as needed. Birds will run around on top (which will dry most of the time). Way down below, the hay will start to compost and rot.......droppings actually helping the process along. And no smell. In this process, you want no acid to kill anything. You want the bacteria, molds and fungus working for you to break things down.
But it will also help if the center is not a bog/depression that ponds water. Birds should be placed on a site that resembles an inverted bowl....one in which water runs off from vs. an upright bowl that traps and holds water.
But it will also help if the center is not a bog/depression that ponds water. Birds should be placed on a site that resembles an inverted bowl....one in which water runs off from vs. an upright bowl that traps and holds water.