You put a box up with some optimism, and two springs later nothing has happened. It is a specific kind of disappointment and it usually has a specific cause. Here they are, roughly in order of likelihood.
The box is too new
The commonest explanation and the easiest to accept. Birds are cautious about novelty, and a bright new box that appeared in March looks exactly like a change in the environment.
Boxes are frequently ignored in their first season and used in their second or third, once they have weathered, greyed and stopped smelling of new timber. If yours is in its first year, the answer may simply be patience.
You can help by putting boxes up in autumn rather than spring, so they weather over winter and get discovered as roosting spots before the breeding season.
Your garden has fewer territories than boxes
A common misunderstanding. Putting up four boxes does not produce four families. Most garden birds are territorial in the breeding season and a typical small British garden supports one pair of a given species, sometimes two.
If you have several boxes for the same species and only one is used, that is not failure. That is the garden being full.
Disturbance
Birds abandon sites where activity is constant and close. A box above a patio table used every evening, beside a shed door, or on the route to a washing line will be assessed and rejected.
The threshold is lower than people expect, particularly during the prospecting period in late winter when the decision is made. If your box is somewhere you pass daily, that alone may be the answer.
Predators you have not noticed
Cats are the obvious one, and the garden may be visited by cats you never see. Look for the launching points rather than the cat: a fence top, a shed roof, a low branch that gives access to the box.
Grey squirrels are the other. If the entrance hole looks chewed or enlarged, squirrels have been at it, and birds will not use a box a squirrel can enter. A metal hole plate solves it.
The hole is the wrong size
If your garden has house sparrows and your box has a 25mm hole, sparrows cannot use it. If you hoped for blue tits and the hole is 32mm, great tits or sparrows may have taken it instead and blue tits will look elsewhere.
Match the hole to the birds you actually have, which means watching what visits your garden before choosing. Our hole size guide lists the diameters.
The box is unsuitable inside
Two things to check. Depth below the hole should be at least 125mm, or the box is too shallow to be safe. And there should be no perch, which invites predators.
Also check drainage. A box without small drainage holes in the floor holds water, and a damp box is rejected. So is one without ventilation gaps near the top, which overheats.
Aspect and exposure
A south facing box in an open position gets very hot on a summer afternoon, and birds know it. A west facing box takes the weather. If the box faces anywhere between south and west with no shade, that is worth correcting before anything else.
Old material inside
A box left uncleaned holds last season's nest, which harbours parasites, and birds frequently avoid boxes that were used the previous year and not cleared. Cleaning is both a welfare matter and an occupancy one, and the legal window for doing it is covered in when to clean a bird box.
What to do next
If two seasons have passed, move it rather than replacing it. Different aspect, more height, further from the path, a quieter corner. Moving a box costs nothing and changes several variables at once.
And accept that gardens differ. A garden with little cover, few insects and heavy cat traffic will struggle regardless of the box. Planting for insects and cover does more for garden birds over five years than any number of boxes.
Our decorative seagrass bird boxes and carved tree trunk houses are shelters rather than certified nest boxes, and are used for roosting rather than broods, so they are not part of this diagnosis.
Questions people ask
How long before birds use a new nest box?
Often not until the second or third season. New timber looks and smells like a change in the environment, and boxes are frequently ignored in their first year.
Why is only one of my bird boxes used?
Because most garden birds are territorial in the breeding season and a typical small British garden supports one pair of a given species. Several unused boxes usually means the garden is full rather than the boxes are wrong.
Does human activity stop birds nesting?
Yes, more readily than people expect. A box beside a patio, a shed door or a daily route will often be assessed and rejected, especially during the late winter prospecting period.
What if the entrance hole looks chewed?
Grey squirrels have enlarged it, and birds will not use a box a squirrel can enter. A metal hole plate fitted around the entrance prevents it.
Should I move an empty box or replace it?
Move it. A different aspect, greater height or a quieter corner changes several variables at once and costs nothing.
