Apartment occupants complained about a continuous Norway rat and mouse problem in their building. Traps, bait, and tracking powder previously had been used to kill the rodents. During the last inspection of the apartments there was no evidence of a continuing infestation. Although no rats or mice were seen by the residents, they heard them scratching around in the enclosed ceiling over the kitchen and bathroom.
Further investigation revealed that the area where the sounds were heard housed the vents for the stove and the bathroom exhaust fans. The fans’ exhaust ducts were vented to the outside of the building. An outside inspection revealed that sparrows were nesting in almost every exterior vent.
The birds and their nests were removed from the vents, and the nesting area inside the vent was treated with a residual insecticide to kill any bird mites and other pests associated with the nests. The vents were screened with 1/4-inch hardware cloth.