The box can be opened from the end of October and cleaned out. Empty out old nest material and any unhatched eggs and clean the inside of the box with boiling water (which should kill most parasites that may be lying in wait, ready to infest next year’s brood). In cases of severe parasite infestation it may be necessary to use one of the less harmful insecticides, such as pyrethrum powder, but this should be avoided unless thought absolutely necessary.
A small handful of wood shavings placed in the box may encourage some birds to roost in it during the cold winter nights. Don't use straw as this will get damp and turn mouldy in the box over the course of the winter.
Providing a safe environment for nesting birds
Robin on a rock
Copyright John Kennedy
Copyright John Kennedy
If birds take up residence in your bird box you should resist the temptation to keep having a quick peep, as this could result in the parents abandoning the nest. Instead, watch the comings and goings of the birds from the safe distance of your kitchen window: they will behave more naturally and you will enjoy and learn more this way. Attacks by predators can also sometimes cause parent birds to desert their eggs or chicks.
Bird boxes can be afforded some protection against predators by fixing a metal plate around the entrance hole. Alternatively, bundles of gorse tied round the tree above and below the box offer protection from most mammalian predators. Do not put a perch on the birdbox; it is of no use to the nesting birds and simply gives predators easier access to the eggs or chicks inside.
Source Garden Bird Detectives Exhibition courtesy of BirdWatch Ireland