Abstract: The invention relates to nest boxes for birds or animals and proposes that the nest boxes comprise a sleeve with a body rotatable therein. The sleeve and body are in plastics material, and the sleeve has a cut-away portion while the body has bird or animal access apertures therein. The body can be rotated inside the sleeve to bring any one of several apertures into register with the cut-away portion so that the box can be adapted for the accommodation of different sized birds or animals. The invention also provides a C-shaped plastics material clip which is to be used for mounting the nest boxes, the clip being of resilient material such as plastics so that it can be sprung over a tree branch or a tree trunk or for example a fall pipe on a building. This clip may be of thicker material at the portion opposite the slot for reinforcing purposes and may be attached to a conventional nest box or to a nest box according to the invention.