Black-capped Chickadees readily nest in birdhouses, especially when the box mimics the small tree cavities they naturally use. In the wild, chickadees usually nest in small holes in decaying trees or stumps, and they will even excavate their own cavity in soft wood. Because of this, they are very willing to use properly sized nest boxes placed in suitable habitat. A chickadee pair typically fills the cavity with moss and soft materials like animal fur, feathers, or plant fibers before laying 5–8

Black-capped Chickadee Nest Building Timelapse