I took the time last week to take down the bird boxes and give them a bit of maintenance. First task is to remove all the old nest material which will most likely be full of insect pupae and larvae. Place this in the garden where the Robins and Dunnocks can get to it.
Next I usually sterilise the inside with near boiling water to take care of any parasites and their eggs in the nooks and crannies. The parasites will return later in the season but it gives this year’s nesting pairs a good start. If you want to be really meticulous you can also give it a bit of a scrub with an old kitchen brush. Set aside to dry for a day or two.
Once dry set to any repairs needed such as making sure the fixings are still sound (adding a nail or a screw where loose). This year I have had to add an new entrance hole cover to one box as a woodpecker had been pecking at the entrance and enlarged it significantly (presumably to get at the insects post fledging).
All that remains is to refix them to the trees or the walls and wait for the first inspection of your efforts!