When to Put Up a Nest Box (And Why Most People Are Too Late)
Almost everyone puts their nest box up too late. By the time the weather is pleasant enough to feel like a gardening weekend, the birds have already chosen where they are nesting.
The short answer
Late winter. February in most of the United States, and January in the warmer south. If you are reading this in April, put it up anyway \u2014 you may catch a second brood or a late pair \u2014 but aim earlier next year.
Why so early
Cavity-nesting birds do not find a site and build the same week. They scout. Chickadees, titmice, wrens and bluebirds spend weeks investigating holes, going in and out, assessing whether the entrance is the right size and whether the location feels safe.
A box that appears in March enters that process late. A box that has been sitting quietly through January and February has been noticed, checked, and already counted as an option.
There is a second reason. In cold weather, chickadees and titmice will roost in a nest box overnight for warmth. A bird that has slept in your box all winter is very likely to nest in it come spring.
Where to put it
Five to ten feet off the ground is right for most garden species. Higher is not better and makes cleaning it out a chore.
Face the entrance away from prevailing wind and driving rain \u2014 in most of North America that means pointing it east or north. Morning sun on the entrance is welcome; full afternoon sun on a dark box in July is not.
Mount it on a post or a pole rather than a tree trunk if you can. Trunks are highways for squirrels, raccoons and snakes. A smooth pole with a baffle is dramatically safer.
Keep boxes apart. Most cavity nesters are territorial and will not tolerate a neighbour twenty feet away. If you want several, spread them out and vary the habitat.
The hole size decides the tenant
Entrance diameter is the single most important specification on a nest box, because it determines which species can use it and which predators cannot.
Roughly: 1 1/8 inch suits chickadees and wrens. 1 1/4 inch brings in titmice and nuthatches. 1 1/2 inch is the bluebird standard. Anything larger starts admitting starlings, which will evict smaller birds.
There should be no perch below the entrance. Perches do not help the birds that belong there \u2014 they grip the wood directly \u2014 and they give predators and starlings something to stand on.
Clean it out
Old nesting material holds parasites. Clear the box out in late autumn once the season is finished, or in very early winter before scouting begins. A stiff brush and no chemicals.
Then leave it alone
The temptation to check is enormous, and every time you open the box during nesting you risk the pair abandoning it.
This is the honest argument for a camera inside the box rather than a lid you keep lifting. You see the nest built, the eggs arrive, the hatching, and the morning they go \u2014 without ever disturbing any of it. It is also most of what happens in darkness, which is why night vision matters more in a nest box than anywhere else in the garden.