I've been making space for a small greenhouse, which involved cutting into a slope a little way, exposing a few inches of clay 'cliff'. There have been quite a few bees buzzing around, and appearing to make holes in this clay surface. Any ideas about what variety/varieties of bees these might be? Very pleased to see them.

I did almost the same thing three years ago

viewtopic.php?f=8&t=6755&p=66781&hilit=bees#p66781

If you put "bees collecting clay" into Google you get various discussions about Mason Bees.

Ah. Interesting, Geoff. Without watching them too closely, I has assumed they were burrowing tunnels to lay eggs. But finding damp clay to seal their nests elsewhere makes sense. At our last garden we had a nesting box for mason bees which worked very well, once we had found a way of protecting it from woodpeckers...Many thanks!

My Mason Bees are under my lounge floor again this year. I had a box for them but were attacked by Lesser Spotted Woodpeckers three years on the go and I then put a wire mesh which was well large enough for them to fly through but they obviously didn't like it. They found a broken floor vent and they stream in and out for a time and then they disappear until the next year.
JB.

Following Geoff's advice, I had a little browse on the internet. One thing I picked up was that mason bees need damp clay verging on mud. As the original bank I had been excavating dried out pretty quickly, I put a couple of lumps of clay in a large plant pot saucer and gave them a good soak. The bees seemed very happy with that.

Speaking about woodpeckers I've just noticed that the lesser spotted woodpecker is again making regular visits to the fat cages in our garden so possibly she has a youngster nearby. I didn't realise they ate bees. Does this mean she might start trying to devour the bumble bees which have colonised in a blue tit nesting box nearby?