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Dragonfly Research

Keeping up with the dragonflies

Honours student tracks insects to learn about migration

Ashley Pidwerbesky, Honours student U of M., holding a dragonfly she caught just before applying the tracking device. On the boardwalk at Oak Hammock Marsh. Image submitted July 18, 2018 for Martin Zeileg Winnipeg Free Press story.

If you’ve wondered how scientists track the migration patterns of dragonflies, they use tiny transmitters that are glued to the insect’s bellies.

From the roof of the Oak Hammock Marsh Interpretive Centre, Ashley Pidwerbesky knows that somewhere out there are several dragonflies with tiny radio transmitters, Motus nanotags, that she has attached to them.

She has climbed onto the roof to adjust two directional antennae mounted on an eight-foot-high aluminum tower.

Pidwerbesky, 22, a fourth-year honours science student at the University of Manitoba, is investigating the migration of two international migrants: purple martins (Progne subis) and their prey, the common green darner dragonfly (Anax junius).

Pidwerbesky and Kevin Fraser, an assistant professor in the U of M’s department of biological sciences and head of the Avian Behaviour and Conservation Lab, designed the study together.

Pidwerbesky spoke about her project at the marsh’s Dragonfly Festival on Saturday.

“This opens up so many possibilities with regards to expanding our knowledge of birds and dragonflies in real time, where they go and what they do,” Paula Grieef, the head naturalist at the marsh, said about Pidwerbesky’s research.

Fraser noted that he and his students have been tracking purple martins for a number of years, both locally and on their migrations to South America.

“Through studies here and in the region, we’ve realized that purple martins are preying mostly on large dragonflies, both to feed their nestlings and themselves as the season progresses,” he told the Free Press during the rooftop interview at the interpretive centre.

“We’ve come to recognize that most of the dragonflies that they’re feeding to their young are migratory. They may migrate along some of the same routes and possibly use some of the same stopover locations as purple martins.”

Manitoba has at least 98 species of dragonflies and damselflies, according to information found on the Nature North website. Some species of dragonflies are migratory, Fraser said.

“Green darners are the ones we’re tracking here,” he added. “They may migrate in late August and early September as far as the Yucatan Peninsula in Mexico.”

Fraser pointed out that, contrary to what many people believe, purple martins aren’t big consumers of mosquitoes.

“Most of what they’re eating are these large dragonflies,” he said.

Pidwerbesky and three or four fellow students from the lab employ butterfly nets to catch the dragonflies.

She uses super glue to attach a .26-gram tag, with a slender antenna, onto the ventral side (belly) of the dragonfly, which tip the scales at about one gram.

“Then, I hold them between my fingers and I have a little envelope that I put them in and put a paperclip to hold them in place,” Pidwerbesky said. “Then, I can weigh them. I have 50 to put out for the whole season. So, I’m putting 10 out right now, and I’m going to track the daily activity levels of these dragonflies.”

She also will be attaching Motus nanotags onto purple martins, both nestlings and adults, to compare the timing of their departure with their dragonfly prey.

Her project is supported through a faculty of science undergraduate student research award, as well as funding from the National Sciences and Engineering Research Council grant and from the Canadian Foundation for Innovation.

Martin Zeilig is a Winnipeg writer.

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