Use a soft hardwood like cedar or pine—both are durable and won’t rot quickly. If the wood’s been reclaimed, rinse it thoroughly and let it dry fully to avoid mold. For the glue, a simple casein paste made from milk and a bit of vinegar works well; it dries strong and is non‑toxic. Another option is a thin layer of beeswax mixed with a small amount of pine resin; it bonds gently and is safe for feathers. Keep the corners rounded, give the house a small roof overhang to keep rain off, and leave a little space at the bottom so insects can climb out. That should make a cozy, bird‑friendly home.