Mason bees lay nest in holes. Hotels are bundle of tubes mounted on wall. It is supposed to be important get goods ones, which seem to have wood trays instead of tubes, but I don't have a source on those. Some people bring the full hotels inside for winter but I get mild winters and figure bees know what they are doing. Then the bees emerge in the spring and lay eggs for winter. The tubes need to be cleaned or replaced, but not sure when.

Thanks for reminding me, I've been meaning to put up a mason bee hotel. I hope not too late.

Most other native bees are ground nesting. Leaving bare earth or brush piles can help.

Unfortunately, I think we missed the window for this year. It sounds like mason bees seal up cocoons in early summer.

I found page on making wild bee sanctuary: https://davidsuzuki.org/living-green/how-to-grow-a-wild-bee-.... And one on mason bees: https://davidsuzuki.org/living-green/how-to-support-mason-be....