Spring is here, and swallows, nuthatches, bluebirds, and other cavity-nesting birds are looking for suitable places to raise their young. Many of you have already put up or will soon be putting up nest boxes to encourage these prospective families to nest in your neighborhood.

But nest boxes come in many shapes and sizes, and choosing which nest box to build or buy can be overwhelming. To help you sort through your choices, the Cornell Nest Box Network staff is offering a crash course in the anatomy of a good nest box.

We have dissected and labeled a nest-box specimen (Generic representativii) to show the basic features a nest box should have to make it functional and safe for its occupants. Please note, the specimen does not take into account certain nest-box preferences that people may have. For example, some people prefer boxes that open from the top rather than the side. Personal preferences notwithstanding, good nest boxes have the basic features shown below.