The depth of winter is a good time to build nest boxes for cavity-nesting birds. Gather some recycled boards and a few hand tools. Old cedar or redwood fence boards are durable and easy to work with, but any type will do. Once you have a cutting plan and a workable prototype, cut out several. They are easy to assemble, especially if you pre-drill the holes and use screws. This makes a good family project.
There are many good reasons for placing nest boxes in the garden, yard, neighborhood, and throughout the countryside. One is that natural cavities are disappearing as old trees disappear from the landscape. The second is that native cavity-nesting birds face intense competition, especially in human-occupied areas, from two aggressive alien species-- starlings and house sparrows (English sparrows). Another is that the presence of the native birds, especially around your garden, will help balance out the insect populations.
Will placing a few nest boxes about the property really have any beneficial effect on native birds? It certainly will on the birds that use them.
The illustration below is a page from my hand-lettered textbook that I used for a university service-learning environmental science course.