In message , Michael
Bell writes

Ah! A lady who knows something that I want to know. My daughter gave
me a bumblebee nesting box for Christmas and I followed the
instructions which said that a mouse nest should be put in the nesting
box to attract bees, so I got my local pet shop to stable his mice
overnight in hay and put that hay into the box (Ah, the obligation
that some gifts put on you!), but no bees settled in it. What more can
I do? It'll have to be next season now of course.

Michael Bell

I'm no expert, but the last time blue tits nested successfully in one of
my nest boxes, there was a real battle between the tits and a large
bumble bee which tried to claim the box, so there could be something in
the theory, though the material they used was softer than straw.
I have some amusing video clips of the female tit dodging as the bee
emerged from the box, but the birds won in the end, against the
predictions of some birding people.
I could find no evidence of a bee's nest when I cleaned out the box,
which had four dead chicks, against the four I saw fledge.
--
Gordon H