This is also a good time to look over the house and make sure the hardware is still firmly in place and the panels are not pulling apart. Some birds, such as wrens and bluebirds, are multiple brooded. For these species, cleaning out the nesting material between broods is recommended so that the birds will keep using the nest box. Although a few studies have shown that bluebirds prefer houses with old nests, it seems preferable to remove nests that may be heavily infested with parasites that can weaken or kill baby birds. Problems Things do not always go as planned when we put out birdhouses.
Most problems arise from competition between different species for a house.
Both House Sparrows and European Starlings are fierce nest competitors that are capable of driving away many native bird species. If starlings get into houses with larger entrances, continual removal of the nesting material may dissuade them. Unfortunately, starlings are tenacious, so repeated efforts may be required. If starlings succeed in taking over a house, try erecting another house nearby so that a different species has a chance to use it. House Sparrows generally present more of a problem than starlings because they can squeeze into smaller holes.