Nesting season may arrive early this year if the recent springlike weather continues. I thought I'd better revivify the bird box I made a few years ago. Last year the small hole was enlarged considerably, probably gnawed by a grey squirrel raiding the eggs. So I stuck a wooden slat over the front and drilled a 28mm hole in it. Metal plates with different size holes are available; I might retrofit one which would hopefully prevent a recurrence of the same problem.

 The RSPB recommends the following diameters: 25mm for blue, coal and marsh tits. 28mm for great tits, tree sparrows and pied flycatchers. 32 mm for house sparrows and nuthatches. One year the box was colonised by tree bees!

 I considered making or buying a new box but I reckon birds don't like the smell or feel of new wood. After all boxes are a substitute for natural nesting sites e.g. in tree trunks. For that reason I didn't varnish the box with a synthetic or solvent based wood preserver when I constructed it. If I remember rightly I used walnut oil instead.

 Boxes should be placed to avoid overheating with too much direct sunlight and allowing for a certain amount of shelter from the elements.