Somebody at home?

Of course, this entrance is inviting
for every bird to just move in,
possibly even without fighting
for such a home, an easy win.

Someone, however, has prepared
this place as his or her own nest,
and not one trouble has been spared
to carve a hole the very best.

So before simply moving in
one carefully should knock at doors,
for an invasion is a sin
and not at all a noble cause.