‘Backpacks’ may hold key to purple martin mystery
Scientists try tracking as bird numbers decline
OTTAWA — Putting a “backpack” on an unwilling purple martin is just about as tricky as it sounds. Yet Nature Canada hopes doing so might shed light on the calamitous decline in the birds’ numbers in Ontario in recent years.
“The population is just plummeting,” Nature Canada spokesman Paul Jorgenson said Tuesday at Nepean Sailing Club, where one of the largest colonies of purple martins in the region nests in two highrise “bird condos.”
Since 2005, the number of purple martins in Ontario has dropped from about 25,000 to an estimated 15,000 today. Similar declines have been recorded across Eastern Canada and the U.S. northeast.
Purple martins — which nest only in man-made houses throughout much of North America — are the largest of nine swallow species that breed in Canada and the United States.
“We have no idea whether the problem lies here, in their wintering grounds (in Brazil) or somewhere in between in transit,” says Jorgenson. “This is really one of these big mysteries that we’re trying to solve.”
To that end, Nature Canada, in partnership with York University and the University of Manitoba, has launched an initiative to track 65 purple martins from Ottawa and the Kingston area.
Similar projects are under way in the United States and British Columbia, but this is the first of its type in Eastern Ontario.
That’s where the backpacks come in. After trapping the birds in their “condo” homes Tuesday, project participants fitted them with one of two tags — a GPS unit or a geolocator — securing them on their avian hosts like backpacks.
“Expertise is required to tie these on,” says Patrick Kramer, head of field work for the project. “Each step has to be done right.”
Two small loops go over the birds’ hips and around their “leg pits,” says Kramer, a PhD candidate at York University.
Twenty of the birds are getting the GPS unit, which enables precise tracking to within about one metre. “We’ll know the tree that they’re sitting on,” Kramer says.
The batteries are so small, the device can only take 10 readings over the next year. So 45 other birds will be fitted with the geolocators, which record light levels every 10 minutes, allowing researchers to plot their approximate longitude and latitude.
“We’re going to discover where these birds go with considerable accuracy,” says Ted Cheskey, Nature Canada’s manager of bird conservation.
That should help researchers better understand the reasons for the purple martin’s decline and lead to improved protection for them, says Cheskey.
“We really hope this project is going to provide some answers that are going to be very, very useful and practical.”
One key objective is to pinpoint where purple martins roost on their annual 5,000-kilometre migration to Brazil. They gather in huge numbers — as many as 50,000 at times. “They even show up on weather radar,” said Kramer.
Some of their roosting spots are along areas that house a large array of industrial wind turbines.
Other potential risk factors include climate change — “the elephant in the room,” says Cheskey — and neonicotinoids, an insecticide linked to the collapse of bee colonies that could possibly be affecting the flying insects that form the purple martin’s diet.
When the birds return from Brazil next April, volunteers trained by Nature Canada will retrieve the data from the backpack tags and send it to researchers at York University for analysis.
Researchers hope to recover about half of the units.
Knowing where the purple martins go is half the battle, says Kramer.
“Then we can start working with people on the ground there and try to protect that area.”
There are plenty of reasons to care about the fate of purple martins, says Cheskey.
“Ethically, we just can’t let species go,” he says. And birds are like environmental sentries. “When their population starts dropping, it’s a sign that something could be going wrong in nature.”
But beyond that, “you can’t help but feel joy when you’re near a purple martin colony. All the chatter going on there — it’s amazing.”