Moss

Does anyone know why I might have clumps of moss strewn about under the guttering all round the house?
Is it birds looking for nesting material, or perhaps looking for small insects?
Whilst collecting it all up for the compost bin I couldn't help noticing how beautiful it was.

Moss By Bruce Guernsey
How must it be
to be moss,
that slipcover of rocks?—
imagine,

greening in the dark,
longing for north,
the silence
of birds gone south.

How does moss do it,
all day
in a dank place
and never a cough?—

a wet dust
where light fails,
where the chisel
cut the name.