The nests of most birds harbour fleas and other parasites, which can remain and infest young birds that hatch the following year.
Maintaining your box
We recommend that old nests be removed in the autumn, from September onwards once the birds have stopped using the box.
Use boiling water to kill any remaining parasites, and let the box dry out thoroughly before replacing the lid. Insecticides and flea powders must not be used.
Unhatched eggs in the box can only be removed legally between September and January (August-January if you're in Scotland) - and must then be disposed of. Take care to ensure the nest is no longer active as some species can nest right through September.
If you place a small handful of clean hay or wood shavings (not straw) in the box once it is thoroughly dry after cleaning, small mammals may hibernate there, or birds may use it as a roost site.
It is quite normal for a few eggs to fail to hatch, or for some young to die. Blue and great tits lay up to 14 eggs to allow for such losses. Cold weather and food shortage may lead to nest desertion, or to only the strongest young surviving. The death of one parent or interference from animals or humans may also cause desertion.
Watch and Enjoy
Avoid inspecting nestboxes in use, however tempting it may be to take a peek! Simply watch and enjoy from a distance. Only open it up if you've got appropriate skills and experience and are taking part in a monitoring project, such as the BTO’s Nest Record Scheme.
If you want to see the chicks as they grow, you could consider installing a nest box camera before the breeding season starts.