A decade of bumble bee surveys: Part 2 – What’s on the menu?

Posted onFebruary 16, 2023|Bumble Bees, News and Events, Pollinators

A decade ago, Wildlife Preservation Canada (WPC) initiated their Bumble Bee Recovery Program. Through conservation breeding, annual large-scale population surveys, community science, engaging in education and outreach, and collaborating on important research, WPC seeks to be a leader in bumble bee conservation. With several of our North American species assessed to be in decline, it’s critical that we monitor our species.

Are you curious what has come from a decade of bumble bee population surveys in Ontario? Then you’ll like this 4-part series! This is the second installment, which focuses on floral resources that bumble bees use. You can read the first installment here – which provides an introduction to our bumble bee surveys, and a brief overview of what we’ve seen over the last decade (over 26,000 bumble bees, including 20 species –many of which are rare and at-risk).

Bumble bee (Bombus sp) queen foraging on cow vetch (Viccia cracca). Photo: T. Harrison

When our bumble bee recovery team conducts monitoring surveys, part of the data that is recorded is bumble bee behaviour during collection –which is most often foraging. If the bumble bee is collected while foraging, our team then records the plant that the individual was found foraging on. As a result, we have been able to build a large database of foraging resources for bumble bees over the years.

Over the years, we have observed bumble bees foraging on roughly 270 different plants in our surveys!

Below you will see the top 15 plants with the most foraging records, organized in order. This list is inclusive flowers across the blooming seasons; however, it is important to be reminded that our team doesn’t always conduct summer surveys each year, and in general surveys are conducted more frequently in the spring (to collect queens for our conservation breeding program).

Top 15 floral resources with the most foraging records during surveys. Each genus is classified from “non-native” to “native” based on the species within the genus bumble bees have been observed foraging on.

Bumble bees are known to be generalists when it comes to their floral preferences, utilizing a large range of resources throughout the bloom season due to their long-life cycle. However, you are still more likely to see bumble bees on certain flowers compared to others for reasons such as their tongue length (meaning they can access some flowers better than others), and their overall foraging patterns often being linked to the abundance and quality of resources in bloom. From this list you will see that the flower we have seen bumble bees foraging on the most is the common dandelion, followed by willow (Salix species) and honeysuckles (Lonicera species). Wondering what makes these flowers so special? Willow and honeysuckles are abundant resources at their time of bloom, with willow being of the earliest blooming resources for bumble bee queens as they emerge from overwintering. Dandelions can be found just about anywhere when they are in bloom, and often fill the transition stage between spring and summer flowers.

Yellow-banded bumble bee (Bombus terricola) queen foraging on willow in the early spring. Out of the foraging yellow-banded bumble bees we have found, 20% were found foraging on willow; 31% on dandelion, and 7% on honeysuckles. Photo: T. Harrison

If you know your flowers, something you will also notice from this list is that most of these top 15 resources are actually non-native to the region. Although these plants may still be visited frequently by our bumble bees, it is likely due simply to their abundance as they often compare poorer nutritionally to our native flowers. Although our bumble bees are more generalists, it is important to keep in mind that other bees might not be able to expand their palette so much, with some specializing on certain groups of flowers due to co-evolved relationships. Therefore, it is still best to plant a wide diversity of native flowers for bumble bees and other bees.

Tri-coloured bumble bee queen (Bombus ternarius) foraging on Vaccinium species. Photo: T. Harrison

If you’re curious what other behaviours we might find bumble bees doing while surveying, it would be actions like flying or exhibiting a nest-searching behaviour (zig-zag flight pattern, deliberately avoiding flowers) –these kinds of non-foraging behaviours make up about 7.2% of our observations.

We want to thank everyone who has helped contribute to WPC’s annual bumble bee surveys, we couldn’t have done it without you! What will we find over the next decade?

We’ve talked about the bumble bee species we’ve observed and what we’ve found them foraging on, but in our next installment we’ll talk about an interesting trend in surveys. Stay tuned!

Wondering what plants you should plant for bumble bees this year? Click this button to get started.

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Tiffani Harrison

Ontario Program Coordinator – Native Pollinator Initiative

Tiffani joined WPC as a bumble bee conservation field technician in 2017 and fell in love with the work. Since then, she has worked a variety of roles leading monitoring surveys, research projects, and community outreach both in Ontario and Alberta. Currently she manages the field work and outreach components of the Bumble Bee Recovery Program. Tiffani completed her MEnvSc in Conservation and Biodiversity at the University of Toronto and comes from a background of ecology and conservation biology.

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