TRACKING DECLINES
Purple martins studied
About 25 purple martins from a colony at Holiday Beach are now sporting tiny lightweight backpacks as part of a large North American study into the species’ migration habits.
The trackers were placed on the birds last weekend by a team of experts led by Kevin Fraser, an assistant professor from the University of Manitoba and an expert on songbird migration.
Nature Canada launched the Purple Martin Project in 2014 as part of an international effort to understand the reasons behind their significant population decline.
Fraser has been studying the issue longer than that.
The trackers deployed at Holiday Beach are relatively new technology using automated radio telemetry.
The backpack sends a signal every 10 seconds that’s recorded by a network of transmission towers located along the shorelines of the Great Lakes.
“Purple martins are declining steeply like a lot of other swallows and we’re losing them for reasons we don’t understand,” Fraser said.
Fraser and the others hope to learn more about where the martins go to roost and prepare for the 10,000-mile winter migration to South America.
“Do they use one marsh, or 20? That will be all new information we’ll get,” he said. “This will be our first look into what space they need. It’s sort of a new piece of the puzzle.”
Fraser’s team also tagged purple martins at Port Bruce and on Amherst Island near Kingston.
The backpacks weigh just 0.67 grams. They’re designed so the harness frays and unravels allowing the pack to eventually fall off. The battery on each pack lasts 75 days.
An inspection team will return next spring to ensure that no bird is still carrying a pack.
Holiday Beach has about five purple martin houses. The team installed temporary trap doors on the individual nest holes of several, holding them open with fishing line that runs down to the ground like a spider’s web.
When all the birds had crawled into the nest to sleep with their young at night, the lines were snipped and the trap doors closed.
The researchers, along with a number of local volunteers, return at dawn to lower the houses and remove the adults to be measured and tagged.
As aerial insectivores, purple martins feed exclusively on flying insects and their demise would cause ripples across the food chain, according to the Purple Martin Conservation Association.