A surprising find: Imperiled rusty patched bumble bee discovered at Oheyawahi/Pilot Knob during survey

By Leslie Pilgrim

In recent years, the once-common rusty patched bumble bee (Bombus affinis) has vanished from almost 90 percent of its historic range. Experiencing declines so dramatic that the species may be on the brink of extinction, Bombus affinis was recently listed as an endangered species by the U.S. Fish and Wildlife Service. Amazingly, in July, 2016, a single rusty patched bumble bee was detected during a bumble bee field survey at Oheyawahi/ Pilot Knob. The find was thrilling for the partners participating in this ongoing monitoring project—The Xerces Society for Invertebrate Conservation and Great River Greening—as well as the citizen scientist volunteers who helped with the “catch and release” effort that day.

An elusive rusty patched bumble bee on a bee balm flower, in a photography by Sarah Foltz Jordan, Xerces Society

An elusive rusty patched bumble bee on a bee balm flower, in a photograph by Sarah Foltz Jordan, Xerces Society

Minnesota’s Bumble Bees in Decline

While the non-native honey bee is the bee most people are familiar with, an estimated 400 bees native to Minnesota provide important pollination services.  Among these native bees, 20 species are bumble bees—about one-fourth of which are struggling to survive. According to Sarah Foltz Jordan, pollinator conservation specialist with the Xerces Society, bumble bees are a priority group to examine at Oheyawahi/ Pilot Knob for several reasons. “In addition to their well-documented declines and high conservation need, bumble bees are unique among bees in that they can be identified, species in hand, without having to collect them and place them under a microscope,” says Foltz Jordan. “They are also very charismatic—the Teddy bear of the insect world—and people get really excited about looking for them and doing things in their own yards to help these bees.”

The Oheyawahi/ Pilot Knob surveys, made possible with support from the Minnesota Environment and Natural Resources Trust Fund, were designed to educate citizens in bumble bee identification and conservation strategies. They will also help in understanding the range, relative abundance, and foraging preferences of Minnesota’s bumble bees.

Oheyawahi, the hill much visited (by pollinators)

The restoration objective of Oheyawahi/ Pilot Knob was to reintroduce the native vegetation that was most likely present before European settlement, as respectfully as possible given the sacredness of the site. Now, with over a decade of stewardship, Oheyawahi/ Pilot Knob has become a crucial refuge for pollinators. “Pilot Knob is a restored prairie with high quality forage, which provides large amounts of nutrition to several pollinator species, including bumble bees,” explains Sean Wickhem, Great River Greening’s project manager for bumble bee surveys. Because Oheyawahi/ Pilot Knob runs alongside the Minnesota River Valley, its location is key in helping maintain and repopulate natural areas along the river’s path. “The next question is,” continues Wickhem, “why haven’t we consistently documented the rusty patched bumble bee on this site, and how can we alter our restoration and management of Pilot Knot to increase their presence?”

Reversing the decline

The combination of habitat loss, pesticide use by homeowners and farmers, climate change, and the proliferation of pathogens and parasites has threatened the viability of many bee species worldwide.  Oheyawahi/ Pilot Knob offers wildlife an insecticide-free environment, nesting habitat for a wide range of pollinators, and an abundance of native floral resources. Wild bergamot, asters, and goldenrods are among the bumble bee favorites growing at Oheyawahi/ Pilot Knob.

Citizen scientists, like the ones who volunteered the day the elusive rusty patched bumble bee was observed, are invaluable in aiding this research. Volunteers are always needed to help with surveys around the Twin Cities metropolitan area.  Another great way to help bumble bees is to participate in Xerces’ Pollinator Citizen Science Projects, including Bumble Bee Watch, or The Minnesota Bumble Bee Survey. “Before we can help these bees, we need to know where they are, and we need more information,” states Elaine Evans.  Evans is an entomologist who helped identify the rusty patched bumble bee at Oheyawahi/ Pilot Knob, and is founder of the Minnesota Bumble Bee Survey, an organization dedicated to monitoring rare and declining Minnesota bumble bees.

Citizen scientists at work; photograph by Sarah Foltz Jordan, Xerces Society

Citizen scientists at work; photograph by Sarah Foltz Jordan, Xerces Society


“Everyone can help bees, right now,” says Foltz Jordan, who suggests the following:

1) Plant native wildflowers, including species that bloom spring through fall.

2) Plant native shrubs and trees for early season bloom.

3) Leave brush, logs, and unmown grasses around the yard to create nesting habitat.

4) Avoid raking whenever possible. Leaf litter is important for overwintering queen bees.

5) Avoid pesticide use.

6) Display pollinator habitat signage, and talk to neighbors about what you are doing for pollinators.

Click here to watch a brief video describing the discovery of the rusty patched bumble bee at Pilot Knob.

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One Response to A surprising find: Imperiled rusty patched bumble bee discovered at Oheyawahi/Pilot Knob during survey

  1. Chris Soutter says:

    Glad to see a rusty patched bumble bee showed up in the Pilot Knob restoration area last year. Hopefully it is the harbinger of a breeding population.

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