If you decide to build your own equipment Pine is commonly used. Just make sure you paint them with a good exterior paint. Or you can stain them and use a exterior polyurethane. Just keep in mind exterior paints hold up better than exterior polyurethanes.
Cypress and Cedar lumber are great exterior lumbers but you pay a little more for them. Avoid using heavy dense lumber like Oak. They may seem like a good idea until you have to carry/ lift them very much. Let the bees add the weight to the boxes..
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