A group of researchers has been spending the past three weeks capturing, tagging and fitting a small songbird known as a bobolink with geolocators.
Headed up by biologist Rosalind Renfrew of the Vermont Center for Ecostudies, a non-profit scientific organization, the team captured and tagged 40 birds at the Luther Marsh and in the Belwood Lake area.
The geolocators track migration patterns of the birds on their 22,000-kilometre trek from Ontario to several countries in South America, including Argentina, where they stay in the winter. The 35-gram bird has been known to travel up to 1,800 kilometers a day during migration.
The tagging project is funded by Environment Canada, according to Renfrew, and saw the team string up light netting in fields to capture the birds.
“It’s the first time we’re getting year-round locations,” Renfrew said after the team captured its final two birds on June 9.
“We’re figuring out where they go, where they hang out. It’s going to fill in a lot of the gaps. They’re only here about four months, but you don’t know about the other eight months. It’s important to get a bigger picture.”
In Ontario the bobolink is classed as a threatened bird species. The bird, which nests in grassy areas and hayfields, has seen its habitat shrink due to development and more frequent hay cutting practices that endanger birds and their offspring.
Bobolinks can be beneficial in hay fields because they consume large numbers of insects that otherwise can be harmful to crops.
In South America and Cuba the birds are considered a threat to crops like rice and are hunted, captured for resale as pets or harmed by pesticides.
Renfrew said they are considered harmful to some crops because they gather in flocks and can consume considerable amounts of crops such as rice. During the retrieval of some birds in South America it was found their diet consisted of about 25 per cent rice, which farmers consider a threat to their livelihood, Renfrew said.
Bobolinks are also hunted for food.
Each fall, the birds gather in large numbers in southern rice fields, where their habit of eating grain has earned them the name “rice bird.” They are collected as food in Jamaica, where they are called “butter birds,” a commentary on how fat they are as they pass through on migration, according to a bobolink website.
Testing of birds done by Renfrew on trips to South America found about 40% of the bobolinks ingested pesticides.
“In the winter they go to South America and they flock in small areas,” she said. “Because of what happens down there, they’re a pest.”
“In Venezuela they’re considered an agricultural pest,” researcher Dan Kim added.
Measurements of each captured bird are taken along with its weight. At the June 9 capture, Kim, who is associated with Portland State University, collected blood samples to record the bird’s DNA and check for parasites before tagging and putting on the tiny geolocator and releasing the bird back into the wild.
At the Luther Marsh site, discovered bird nests were flagged.
To retrieve information from the $200 geolocators, birds have to be recaptured.
“There’s about a 30% retrieval rate,” said Kim.
Renfrew believes the retrieval rate is good and has created “an explosion of information” for researchers to comb through in order to get a better picture of the bird’s migration habits and locations.
She said the bird usually lays five to six eggs in its nest located on the ground. Bobolinks can live up to nine years, although the average, according to her, is two to three years. Despite the lengthy migration, the birds will return to their nesting area.
“There is a high return rate for birds that nest and are successful,” Renfrew said.
Tagging projects have been done in Wellington County and in New Brunswick. The team had hoped to conduct a similar project in Alberta, but “it didn’t work out,” she said.
The team was issued 40 geolocators, which they used. On one day they managed to capture 16 birds and tag them. The capture was evenly split with eight males and eight females.
“We’re the only people who have done this with bobolinks,” Renfrew explained.
“It’s been fun and it’s been great,” she said of the project here. “This is a great habitat for them.”
