BirdCast: Garden Pests: Mice and Rats

Pest: House Mouse (Mus musculus), Roof Rat (Rattus rattus), Norway Rat (Rattus norvegicus).

Discussion: These three rodent species are often closely tied to humans and will make themselves at home in your home if food and shelter are available. Other than seeing or hearing rodents around the home, common signs include droppings and holes gnawed in cardboard boxes. Openings on the exterior of your home (space around pipes, air vents, etc.) can allow access for those in search of food. Mice and rats will also seek shelter outdoors, especially in brush piles, stacks of firewood, and under thick bushes. All will eat a variety of foods, but the House Mouse and Roof Rat tend to prefer seeds and fruit while the Norway Rat has a taste for meat and insects.

Pesticides Commonly Applied: Brodifacoum (Talon, Havoc), Warfarin (d-Con) and other anti-coagulants.

Physical Controls: Reduce the availability of food in and around your home and plug or cover potential entry points with chicken wire. If you notice a problem, set traps in crawl spaces, attic and/or your basement. For mice, use a cotton ball or peanut butter as bait. For rats, bait a trap without setting it for two to three days. Rat's are weary of new objects, but will loose their fear of the trap after a few easy handouts. After the bait has been taken several times, bait and set the trap. Another interesting method is to set your traps in the middle of a small pipe/cardboard tube. Make sure the diameter is big enough to allow the trap to spring shut. The pipe may help attract mice (which love to crawl in confined spaces) and safeguard traps from unintended victims like birds (for outside uses) and probing fingers.

Bird Facts: 90% of a Great Horned Owl's diet consist of small mammals including mice and rats. Other raptors will also feed on rodents when encountered. Rats poisoned with anticoagulants pose a threat of secondary poisoning to the raptors or other wildlife preying on them. Great Horned Owls kills made up 30% of the reported wildlife mortality incidents involving the pesticide Brodifacoum in the EPA's "Ecological Incident Information System" database. Other raptors (mostly Red-tailed Hawks) made up another 31% of the reported incidents.