Paul Mc Cann wrote:

ISTR that dry bird droppings can metamorphose into
unpleasant/nast/unhygienic dust so a good dust mask probably would not
go astray.

Thanks for all your advice.

It is amazing the quantity of droppings that can accumulate
with a few birds in a couple of years.
Every time I went to cut off their entry it turned out they were nesting
and the children objected to their being expelled.

--
Timothy Murphy
e-mail (80k only): tim /at/ birdsnest.maths.tcd.ie
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland