Do you get damage to your wooden posts and fence panels? Do you see lighter coloured stripes on darker wood like these?
On a quiet, still Summers day you may hear a distinct scraping sound. More than likely it will be one of these helping itself to some of your wood.
I have often heard and seen wasps stripping the top layer of wood fibres to turn into a pulp which they use to build their nests. They seem to use the same few favoured spots and in the past I could see where my old oak fence had been thinned over the thirty years it had been in place.
Recently I have seen bumble bees apparently resting on fence panels in the Sun and assumed they were resting and warming up but this morning as I watched one buff tailed bumblebee I got the impression it was also gathering wood fibres.
I though I could hear it scraping at the surface but that may have been my imagination as there was a lot of background noise at the time and the wood is too new to see any evidence.
6 hours ago