Pest control experts were called in to the Belford Hospital in Fort William after the insects were seen in rooms adjoining the theatre.
A spokeswoman for NHS Highland said it is suspected a bird got into the building while new windows were being fitted.
The theatre is expected to be closed until next Wednesday. Patients requiring minor surgery under local anaesthetic can still be treated in Fort William.
So far no-one has had to be transferred to another hospital, but arrangements have been made to treat those requiring more major surgery and those in need of observation before their procedure at either Raigmore Hospital in Inverness or the Lorn and Islands Hospital in Oban.
Gill McVicar, general manager for the Mid Highland Community Health Partnership, said normal service will be resumed as soon as possible.
She said: "It has been agreed that temporary closure of the facility to allow action to be taken is in the best interests of everyone involved."