Bumble bees are important pollinators. Supporting these beneficial insects by providing suitable nesting sites is a straightforward way to contribute to local pollinator health. Establishing an artificial nest box can offer a home for a newly emerged queen searching for a safe, insulated cavity in the early spring. Success depends on mimicking the natural conditions bumble bees seek, including the physical design of the box, its exact placement, and the materials used to entice a queen to settle.
Designing and Preparing the Nest Box
Construct the nest box from untreated wood, such as plywood or pine, to avoid exposing the bees to harmful chemicals. A common internal dimension for the nest chamber is approximately 6 inches by 6 inches by 6 inches, which provides enough space for a developing colony while remaining compact. Proper ventilation is necessary to prevent condensation, so include a few small, screened holes covered with a fine mesh to deter pests like wax moths.
The entrance hole should be just large enough for a queen to pass through, typically ranging from 5/8 inch to 1 inch in diameter. Since bumble bees do not excavate their own nests or gather external nesting materials, interior preparation is important for simulating a natural site. The box must be lined with soft, insulating material, formed into a small, loose ball with a depression in the center for the queen. Synthetic fibers must be avoided as they can entangle the bees’ legs. Acceptable materials include:
- Natural moss
- Finely chopped hay
- Kapok fibers
- Untreated upholsterer’s cotton
Strategic Placement for Success
The location of the nest box is crucial. Place the box on a firm, well-drained surface, which can be directly on the ground or elevated slightly, between 8 and 24 inches. A spot that receives morning sun but is shaded during the hottest part of the afternoon is preferred, often achieved by facing the entrance hole toward the east or southeast.
Secure the box against movement from wind and ensure it has a protective overhang to shield the entrance from rain. Locating the box near a visible landmark, such as a large tree or a fence line, helps the queen orient herself and remember the location. Proximity to a reliable source of flowering plants is also beneficial, as the queen will begin foraging immediately after establishing the nest. Avoid areas near high foot traffic or within 10 feet of known ant colonies, which can pose a threat to the developing nest.
Using Specific Attractants and Lures
Bumble bee queens often select abandoned rodent burrows as natural nesting sites because they are highly sensitive to the odor of small mammals. The most effective lure is material that mimics the smell of a former rodent nest.
Research has shown that baiting a box with bedding soiled by house mice or using synthetic rodent odor lures can significantly increase the rate of successful colonization compared to unscented boxes. If using natural material, it is safer to use used bedding from a pet mouse or hamster rather than collecting wild rodent waste, which may carry disease. A small amount of this material should be placed inside the nest box, mixed into the insulating material, to activate the queen’s natural nesting instinct. Alternatively, a minute quantity of ammonia can be used to simulate the scent of mammal urine, acting as a chemical attractant placed near the entrance.
Monitoring and Protecting the Colony
The best time to place the nest box outdoors is in the early spring. Once the box is deployed, monitoring for activity should be done discreetly to avoid disturbing any potential occupants. Look for a queen making frequent inspections of the entrance hole, often taking orientation flights to memorize the location before she commits to nesting.
Preventing pests is important, as small mammals and insects like wax moths can be destructive to a young colony. Placing the box on a slightly elevated platform or using wire mesh around the base can help deter small predators. Since bumble bee colonies are annual, the nest will naturally decline by late summer or early fall. Once all activity ceases, typically after the first hard frost, the box should be cleaned thoroughly to prevent the spread of pathogens. Remove old nesting material and wipe the interior down with a mild bleach or soap solution before storing or redeploying the box the following spring.