The Nature House Spare-O-Door can be used to replace any door in your martin house and turn that compartment into a sparrow trap.  When a sparrow enters that compartment an orange door closes giving a visible signal that the trap has been sprung. A removal device is included to remove the live sparrow without opening the compartment.  Traps should be checked frequently as the intention is a humane capture of a live bird.  Compatible with all Nature House Purple Martin Houses.