After the birds left and no new birds started breeding I took down the birdhouse to clean/check the condition of all components. Putting a cork floor on top of the scale turned out to be not so good an idea. The birds used their claws in winter time to turn the cork floor into crumbles. I have replaced the cork now with linoleum (hope this will be more durable). And I have added another coat of linseed oil to protect the wooden panels of the birdhouse. This should hopefully prepare the birdhouse for yet another year out in the field :-) .