Species’ decline unnoticed for decades until 1999
Rusty blackbirds do not have flashy plumage and their songs can be likened to the sound of a VHS tape rewinding or a squeaky door, but they are the focus of birders from Canada to Louisiana this spring as researchers try to find out why their populations have declined dramatically.
The Rusty Blackbird Spring Migration Blitz is going on in Louisiana through March and is part of a larger effort to enlist birders along the rusty blackbirds’ migration route to track what habitats the birds are using and where those are, and even as important, where the birds are not found this spring.
Volunteers are still needed in Louisiana.
Although the population decline of rusty blackbirds is thought to have been going on for decades, it was brought to the attention of ornithologists and birders after a 1999 report was completed. Russ Greenberg was one of the authors of the report.
“He was the person who was the motivator,” Sinead Borchert said of Greenberg.
Borchert is an LSU student working on a master’s degree in wildlife biology and the state coordinator for the blitz efforts in Louisiana.
The report, she explained, got people to look into the rusty blackbird’s population and to conduct more research into possible causes for the decline.
It may seem strange to some people that a blackbird could be considered rare when there are so many red-winged and other blackbird varieties that people see. The rusty blackbird, though, is a little different. It prefers foraging in slightly flooded forests where the bird spends time turning over leaves in search of food, Borchert said.
They breed in out-of-the-way swampy areas in Canada, Alaska and the northeastern United States. Rusty blackbirds prefer areas that don’t normally get a lot of human attention, which is why when they started fading away, no one really noticed.
“It’s kind of an elusive bird,” she said.
The bird was plentiful about 100 years ago, according to Judith Scarl, coordinator of the Rusty Blackbird Spring Migration Blitz and conservation biologist with the Vermont Center for Ecostudies, but it was never monitored very closely, leaving it unclear as to what caused the population decline over the years.
“The peak of the decline seemed to have happened between the 1960s to the early 2000s,” Scarl said, but the species may have been in decline much earlier.
During that 40-year period, Scarl said, it’s estimated the birds’ population declined between 85 percent and 95 percent, although researchers still don’t have a good handle on how many birds are left.
The few publications counting the birds have estimates that range between 158,000 to 2 million birds.
“The general consensus is there is no one cause,” Scarl said. Instead, it’s likely to be a combination of factors, including habitat loss, especially in their wintering grounds of southeastern United States.
“It’s probably this perfect storm of causes,” Scarl added. “It’s hard to know.”
There have been a number of rusty blackbird surveys done in their wintering grounds, which includes Louisiana, but one piece that has been missing is the bird’s migratory route, which includes where they stop, what habitat they prefer and if they use the same stopping points each year as they travel back north to their breeding grounds.
“What they really have no information on at this point is the stopover points — the migration,” she said. So this year, birders in states and territories along the migration routes are being asked to specifically look for the bird and report it under a special tab on eBird.
Scarl said as important as the information provided along the migration route will be, an added benefit is raising awareness about the rusty blackbird and the problems the bird is facing.
The Rusty Blackbird Spring Migration Blitz is a partnership between the International Rusty Blackbird Working Group, eBird, the Cornell Lab of Ornithology and the Vermont Center for Ecostudies.
Information about the spring migration blitz is available at rustyblackbird.org.