The warmth of the mid-April sun is too intense, and I find refuge in the shade of a large bur oak tree trunk. As I’m draining the sweat out of my nitrile gloves (herbicide protection gear), I hear a low-pitch buzzing sound. Moments later, the buzz gets louder, and a large bumble bee appears zigzagging back and forth just a few feet from my face. Satisfied that I’m not a flower, the bumble bee rapidly dives toward the ground, hovers, and then disappears below the surface. A second later it’s back, slowly flying just above the ground in a grid pattern. The queens of spring have awakened; I smile.
Queen bumble bees spend all winter alone hibernating below the ground. She, and other queens, are the only surviving members of the bumble bee colony. All other members, such as workers and males, only live for one season. It’s up to the queen to rebuild the colony. Queen bumble bees are the ultimate in single female power. She has to make a lot of good choices – a safe place to hibernate, find immediate nectar sources after her spring emergence, find and defend a nest location, and raise the first batch of worker bees alone.
We humans are one of the greatest beneficiaries of the humble bumble bees’ activities, as they are critical pollinators of many of the foods we rely on. Logically, one would think, we would work to ensure that they prosper on the landscape. Unfortunately, our land use activities have done just the opposite, causing steep declines in many bumble bee species.
Like all creatures, bumble bees need quality habitat. Good habitat includes nectar sources from snow melt all the way past the first killing frosts. It also includes rough ground with lots of holes and underground voids where queen bumble bees can hibernate and build nests.
Conventional agriculture fields are not good habitat, nor are golf courses, manicured lawns or paved surfaces. Unfortunately, remaining “natural” areas are often not good habitat either due to complete dominance of the plant community by a few invasive species. In Wisconsin, for example, many of our woodlots are completely dominated by dense European buckthorn thickets. This small tree/shrub will eliminate early spring flowers that are so critical for queen bumble bees emerging from hibernation.
Fortunately, scientists have learned much about our native bumble bees, and land managers are putting this knowledge to practice. Ecological restoration activities such as invasive species removal, reintroduction of native flowering species (especially early spring blooming species) and the encouragement of burrowing animal species such as moles and ground squirrels all help bumble bee populations to recover.
For example, after spotting the queen bumble bee, I made note of every blooming species I encountered the rest of the day. For those of you who are not familiar, mid- to late-April in southern Wisconsin is the start of green up. Most trees are still in bud stage (no leaves) and a “green” ground layer is just starting to emerge. The property I was working on has been under ecological restoration for approximately 15 years and is a mix of oak savanna and woodland, wetlands and prairie.
Here is the list: Pennsylvania sedge, wood violet, early buttercup, pussytoes, kidney-leaf buttercup, golden Alexander, prairie smoke, dandelion, Dutchman breeches, blue-eyed grass, violet wood sorrel, cut-leaf toothwort, bird’s-foot violet, wood anemone, rue anemone, blood root, marsh marigold and wood betony.
Other than the dandelion (not native), most of these once-common species are now largely absent across the landscape. If you’re a queen bumble bee living on this property, life is good. Still difficult mind you, nature is always hard, but at least she has a fighting chance.
Most of us can do a few things to help our native bumble bees. If you own a yard, allow some dandelions and creeping Charlie to live, lay off the “whack a mole” games, and convert some lawn space to a mixture of native plants that bloom all growing season.
For the land restoration practitioner, consider the humble bumble as you remove invasive species and aggressive native species that could potentially be used as surrogate nectar sources by the bumble bee. To ensure bumble bees have adequate nectar sources, it may be necessary to throttle the removal of these surrogate nectar sources to a pace that matches desirable native nectar source replacement. For example, several willow species and the thorny American gooseberry can be overly abundant and are often targeted for removal by practitioners. However, they are excellent early spring nectar sources for bumble bees.
The drone of the queen bumble bee fades away, and I watch her disappear from sight. It’s up to all of us to ensure the bumble bee does not disappear forever.