The message
from "TheScullster" contains these words:

We have some ivy at the back of our garden clinging to the side of a
neighbour's garage.
It is already starting to creep into the flat roofing and, being the
sterling fellow what I am, I am inclined to top this off before it causes
real damage.
I noticed this morning that there is a wren starting to build a nest in the
ivy about 2/3 of the way up the garage wall.

The question is: will the wren be frightened off if I cut the top foot or so
off the ivy "carefully".

ISTR, that male wrens build (or start) several nests at a time, so
that the hen can select whichever she prefers. Consequently lots of wren
nests are never laid in anyway; though they may later be used for winter
roosts.

Wrens (like robins) become very bold when they are used to people
around the garden. (We have one at the moment who is always underfoot
when I'm digging, and has no qualms about exploring inside all sorts of
containers and restricted spaces; even underground ).

Janet