Oregon Revised Statutes Property Rights and Transactions § 90.148

The surrender of a dwelling unit may be implied from the landlord's acceptance of a tenant's abandonment or relinquishment of the right to occupy.  The landlord's acceptance may be demonstrated by acts of the landlord that are inconsistent with the existence of the tenancy.  A landlord's receipt of the keys to the dwelling unit or a landlord's reasonable efforts to mitigate the landlord's damages by attempting to rent the dwelling unit to a new tenant shall not constitute acts inconsistent with the existence of the tenancy.  Reasonable efforts to mitigate damages include preparing the unit for rental.