Every year, solitary carpenter bees make themselves at home in our wood window casings. I can see their little bee butts working away in there. The question is, what to do about it?

A window casing hole still plugged with growing bees.
Photo: PKR

Now, I admit, the drainage holes in the windows look mighty inviting. But because the windows open and shut, any growing bees are at risk of getting crushed before they can mature.

I really don’t mind sharing parts of our home with other creatures, and at the end of the season, the remains of the nests and pollen are easy enough to clean away. I know people don’t like the fact that these bees can burrow into wood – but after all, the casing holes are already there, and the bees don’t do any real damage.(It’s indicative of how these bees are viewed that most of the images of carpenter bees that I found were from pest extermination services – it took me a while to find one that wasn’t.)

Still, even our window sill haven is not a particularly safe solution for the bees.

The nests are intricate constructions of single cells for each single egg, with partitioned walls and a lovely supply of pollen for each egg to get a good start.

A solitary bee nest.
Image: All You Need Is Biology

Quite impressive, as long as they’re situated in a good spot.

A vacated nest. I saw one of the new bees emerging from this spot yesterday.
Photo: PKR

Bees of various species are struggling in our corner of France, as elsewhere. If these bees are, as I suspect, Osmia cornuta – a solitary European orchard bee that pollinates fruit trees – then they are not yet considered endangered. But they are in decline in France, retreating to places with less pesticide use. In any case, this year in the spirit of conservation, I set up alternative bee houses with holes of a similar size in front of the favorite window sills.

What did the bees do? They chose the other casings that didn’t feature any manufactured wood homes. So until they’ve all left the nests, we’ll be opening and closing the windows very carefully.

Silly bees.

Next year, I’ll have to try harder to entice them to other nesting spots.

Solitary orchard bees burrow into someone else’s window casing.
Image: Lamiot via Wikipedia