Post by Jen Berlinghof
All summer long, swaths of wild bergamot (Monarda fistulosa) quake in the presence of thousands of native bumble bee wings beating away. These pollination dynamos use a technique called buzz pollination, vibrating their bodies to trigger nearby flowers to release pollen. At the Lake County Forest Preserves in northern Illinois, a similar buzz of excitement arrived in summer 2020 when staff spotted the federally endangered rusty patched bumble bee (Bombus affinis) at Greenbelt in North Chicago.
Fast forward to summer 2021. The hum continues to reverberate after multiple sightings of this keystone species were documented across the county from Flint Creek to Wadsworth Savanna in Wadsworth. While summer’s the height of hive activity, the shoulder seasons—usually defined as May, June, September and October—might be key to the success of the rusty patched bumble bee. This is partly due to the timing, or phenology, of the species’ lifecycle. It’s one of the first bees to emerge in spring and the last to enter hibernation in fall.
While the rusty patched bumble bee became the first federally endangered pollinator in 2017, it’s not the only native bumble bee in peril. Of North America’s 4,000 native bees, many are declining rapidly due to habitat loss, increased pesticide use, disease, and climate change. A pollinator poster child, the rusty patched bumble bee’s populations have fallen more than 87% over the past 20 years. And according to the U.S. Fish and Wildlife Service, it flies the skies of fewer than 1% of its historic home range.
Native bees are critical to native wildflower pollination and the diversity of the food supply for wildlife and humans alike. Which is why there’s a vast conservation effort happening in natural areas, backyards and cities across North America to save the rusty patched bumble bee from extinction.
Wildlife biologists, restoration ecologists, and community scientists monitor and record sightings using crowd-sourcing sites such as BeeSpotter and Bumble Bee Watch to share data. The majority of information involves sightings during late summer and early fall. This is when female workers—their pollen-laden hind legs resembling yellow leg warmers—and male drones can be captured and put on ice, temporarily slowing them down to allow easier identification. After gathering data, bee researchers release the insects so they may continue on with food collection and sperm donation to the betterment of their hives.
And yet researchers struggle to learn more about how those hives actually function. They know the lifecycle of native bumble bees is unique—the entire colony dies out in late fall, leaving behind only a queen, who’s already been fertilized, to overwinter. It’s not totally clear where the vagabond queen hunkers down, but new research leads scientists to suspect she heads into forests to slumber in the crevices of trees. Come spring, she emerges to establish a colony in old mammal burrows or the cracks of tree trunks.
The queen typically times her spring emergence to coincide with the blooming of ephemeral woodland wildflowers. These early-blooming plants provide a much-needed energy boost for the queen, necessary for her work setting up the hive after a long winter dormancy.
But a new study shows evidence of a decline in spring woodland wildflowers, along with an increase in prairie and grassland flowers the rusty patched bumble bee feeds from during summer and fall. Researchers hypothesize this drop in woodland spring blooms might contribute to the fall in bumble bee populations by limiting the queen’s ability to garner enough energy to start a colony. There’s also evidence of climate change implications as the flowering times of plants may start to shift, potentially misaligning the queen’s needs with the availability of nectar and pollen in early spring.
With its long colony life stretching from April through September, the endangered rusty patched bumble bee requires nectar and pollen from a variety of native flowers in prairies and grasslands over spring, summer and fall. Additionally, it needs the safe haven of a healthy woodland to support the overwintering queen. Habitat restoration of these vital ecosystems in the Forest Preserves and other natural areas is critical to help ensure this species survives and thrives in Lake County.
You can help, as well! Plant bee-friendly native plants, avoid the use of toxic pesticides and chemical fertilizers, and contribute to community science monitoring programs such as BeeSpotter or Bumble Bee Watch. Let’s all keep the buzz of native bumble bees going!