Perhaps not the most exciting thing to do, but the time is ripe, according to Anders Wirdheim at Sveriges Ornitologiska Förening (Swedish Ornithological Society).

“These boxes are used mostly in wintertime by a variety of smaller bird breeds. The most common ones being blue tits and great tits, but I know of cases where ten wrens have been found in one nesting box,” Wirdheim explains. What’s best for the nesting birds? Wirdheim says it has not been scientifically proven, but some studies show birds prefer older boxes rather than new ones, waiting for the boxes to get a bit of patina. “It’s also not clear whether the boxes ought to be cleared out,” he continues. “Natural birds' nests are never cleared by humans, for instance, and there’s no proof that there’d be more parasites in an un-cleared box. However, clearing out a nesting box means the box can be used longer." Old nests attract dampness which leads to more mold and faster decay.