The Bird Brick by designer Aaron Dunkerton places birdhouses in walls. Dunkerton created a series of bricks with cavities to act as a shelter for birds. Since urban nesting sites have decreased, building birdhouses into walls helps to keep the avian population up.
The bird brick consists of a series of blocks arranged to form a circular cavity. Filling the cavity is a hollow and removable brick. The brick was made to be removable to allow it to be cleaned. According to Dunkerton, the cavity must be cleared every 2-5 years. All you have to do is twist out the brick, remove any debris and place the brick back into the cavity.
Dunkerton's brick design has been shortlisted for a Future Pioneer Award at New Designers 2013.