The message
from Pam Moore contains these words:

To cap it all, this morning I admired a
good 3 inch shoot on a seedling delphinium, up on the bonsai shelf,
and now the shoot has totally gone; no sign of life at all, and soil
everywhere!

Same here but with a small Linum seedling we had been given
by a friend. Also seem to be trying anything in a tub, trough or pot
that looks remotely useful for nest building. Rather more than annoying
since we have plenty of moss in the lawn. ;(

Is it the fact that the ground is dry and hard and the birds cannot
dig in it? I can think of no other reason.

... or is it peculiar to Bristol???

Jennifer - in Bristol