Summer sends Canada’s largest college campus into a slumber. While the years have populated York University’s vast Keele St. grounds with more and more new buildings, July and August still denude the 457-acre property of people.

But bumblebees abound.

And there one recent morning — in a sweltering meadow on the school’s southeastern-most edge — was PhD student Victoria MacPhail plucking them up, one by one, with an artful twist of a net.

“This is a common eastern bumblebee,” said MacPhail, 37, showing off her first, agitated capture in a clear plastic vial.

“It is the most common bumblebee you’ll find around here ... and it seems to be loving urban areas in particular,” she said.

This stripe-rumped Bombus impatiens is not only thriving in southern Ontario, but is now spreading its labouring wings across large stretches of Western Canada.

Like their honeybee cousins, however, many bumblebee species are in trouble — some seeing population declines so steep they’ve all but disappeared from longtime habitats.

“We’ve actually found that probably about a third of our bumblebees are in decline,” said MacPhail, her eyes scanning the grassland from beneath a Tilley hat.

And MacPhail is an important part of a York-led project that is trying to help address these plunging numbers by recruiting thousands of ordinary citizens from across North America to the cause.

Known as the Bumble Bee Watch, the project now employs some 8,300 “citizen scientists” who are on the lookout for the insects in backyards, parks, campgrounds and neighbourhoods throughout the U.S. and Canada.

“We’re trying to figure out where are our rare species, where are our common species (and) how are they doing,” said MacPhail, whose doctoral thesis is centred on the project.

“Are they doing things that change their range, are they expanding their range, contracting their range, what flowers are they feeding on, what time of year do they come out — all these basic questions about bumblebees.”

There are no known, but almost certainly multiple explanations for the decline of bumblebee species — such as the Rusty Patched variety once abundant in southern Ontario, MacPhail said. Climate and habitat changes, pollution, pesticides and parasites and other ailments could be counted among the explanations.

“This is the 15th year since we’ve last seen this bumblebee here,” MacPhail said.

And it’s only by answering the basic, Bumble Bee Watch questions that effective conservation efforts can be launched, said Sheila Colla, an environmental scientist at York and founder of the project.

Expanding the number of eyes — and cellphone cameras — that can be trained on the creatures has helped to fill in both mapping and knowledge gaps on their locations, movements and behaviours, said Colla, who started the project in 2015.

“I’ve been working on bumblebees since 2003 (and) I spent a good 10 years just driving around looking for some rare species and not really finding any,” she said.

“So ... we kind of thought maybe it makes more sense to get more eyes on the ground.”

Employing a Bumble Bee Watch internet app, those amateur eyes have so far produced some 41,000 recorded sightings that include all but a half dozen of the 46 known species of the insect.

Importantly, the submissions also include such things as the types of flowers the bees are feeding on, the times of year and day they are active and, on rare occasions, the locations of their elusive nests, MacPhail said.

Compared to the honeybee, the bumblebee is something of a lout in the nest-building department.

Whereas honeybees can organize themselves in the tens of thousands to build vast hives of perfectly formed, hexagonal-celled comb, the bumblebee constructs lumpy abodes — of a few dozen inhabitants — hidden furtively on or in the ground.

“They’re more like little pods of wax ... just sort of a haphazard,” said MacPhail, adding that — unlike honeybees — bumblebees only live for one year and don’t require large stores of well-sorted honey to see them and their young through the winter.

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Like their honey-making counterparts, however, bumblebees are crucial pollinators, she said.

Many apple orchard owners import honeybee hives onto their properties each spring to pollinate their trees, “and they get apples and they say ‘woohoo we got pollination it must have been the honeybees,’” MacPhail said.

“And the honeybees may have done a little bit of the work, but it’s probably the bumblebees (and other species) that are out there doing most of it.”

The York project closely resembles the much larger eBird initiative that has collected more than 100 million bird sightings from tens of thousands of watchers around the globe.

However, unlike the volunteer eBird participants — many of whom are experienced birders — most bumblebee watchers know little about the insects they’re scouting.

Thus the data they provide the project is relatively raw and it’s left to Colla, MacPhail and other academic experts to curate — relying on often subtle colouring and facial differences for identification.

As part of her thesis paper, MacPhail will look at the effectiveness of such amateur inputs into mainstream science.

But, as on her morning prowl at York, MacPhail is still actively engaged in the search and identification process.

Armed with a net, pockets full of plastic vials and a freezer block-filled pouch, she can collect hundreds of bees on a single forage.

With an almost flawlessly sting-free technique, she’ll place specimens in the vials, which she marks on a masking tape patch with the species’ name and type of plant it was feeding on.

She then places the agitated bugs into her pouch, where the cooling packs calm them down until she can get back to a nearby computer to record all relevant details.

The bees are then released, none the worse for ware.

And MacPhail, who has been studying bumblebees for more than a decade in both professional and academic settings, has abundant enthusiasm left for her fieldwork chases.

“If I see a common eastern I might say ‘ehh,’” she said. “But if it’s something rare, something different, I’ll jump logs and ditches to go after it.”