By LINDSAY DUNBAR
Capital News Service
LANSING – Endangered birds in Michigan are sporting tiny locator backpacks to help determine how they get to their winter homes.During the summer, Kirtland’s warblers nest only in certain areas of Michigan, Wisconsin and Ontario, according to the Department of Natural Resources (DNR).
In Michigan, they are found in 13 counties, from Lake Huron west to Kalkaska County and from Presque Isle County south to Ogemaw County.
During the winter they migrate south to the Bahamas.
The question is, how do they get there? And without knowing the birds’ migration patterns, it’s hard to safeguard their other important habitats, conservation officials say.
“Migratory activity is important,” said Daniel Elbert, an endangered species biologist with the U.S. Fish and Wildlife Service based in East Lansing. “Climate change and weather patterns could have repercussions on breeding grounds.”
New developments in tracking animals allow researchers to reconstruct the movements of the tiny birds, according to a pilot study.
The birds winter in the Bahamas, but their exact locations are still unknown. What researchers are attempting to learn about the warbler is how it reaches these locations and what other pressures are on it, said Mike Donovan, a DNR wildlife habitat resource specialist.
The tiny devices are called light-level geolocators. They measure changing light intensity over a period of time.
“This technology is for continental movement, not local,” said Elbert. It’s needed because although the bird’s winter home is known, the bird is so rare that there are few reports on how they got there.
The locators measure the time the sun rises and the time the sun sets. That data later can be analyzed to recreate the bird’s migration routes and winter home locations, according to the pilot study.
The battery-powered solar cell locators last about nine months, Elbert said.
To avoid hindering the bird, the locators stick to a 5 percent body weight rule researchers use when putting tracking devices on animals.
“You have to think about these things when tracking wildlife,” Donovan said. “How do I capture, what am I going to put on it and how am I going to get the data?”
The longer birds stay in a certain area, the more precise the location.
Elbert said, “It’s a conservation concern. The flight of Kirtland’s warbler is tied to human development and human interaction. Due to loss of habitat, humans have had a very active role in decline of this species, but can also protect it with intervention.
Donovan said, “Warblers carrying the unit can be located within hundreds of kilometers. Our goal in this study is to understand the relative path and if birds are wintering in the Bahamas.”
These endangered birds are picky nesters when arriving at their breeding grounds in the north. Weighing only about half an ounce, they nest on the ground underneath vast acres of jack pine trees.
“Called the ‘bird of fire,’ it relies on jack pine trees between 5 and 15 years old,” Donovan said. “Jack pines regenerate after fire.”
That’s a problem because people don’t like fires and jack pine fires are intense and big, he said
According to the DNR, the agency used to do burns but controlled burning is a scary proposition. The 1980 Mack Lack fire that burned about 25,000 acres and killed one person in Northeast Michigan ended the prescribed burning program.
“That burn got so big, it ended up being the comeback of the warbler,” he said. “This showed us the importance of size of the habitat – we were managing it at too small of a scale.”
Now, the DNR cuts and plants jack pines in patterns that mimic a fire to manually produce the warbler’s habitat, Donovan said.
As for the Kirtland’s warblers’ backpacks, Elbert said the geolocator technology is great because young jack pines allow in a lot of light. That gives the geolocators the ability to capture the light more easily, which wouldn’t happen for a species that lives deep in a forest.
Michigan’s conservation efforts have helped increase the bird’s population, experts say
“In 1990 we were at 400 singing males in the entire population and now we’re over 2,000,” said Donovan.
There are risks to this study, Donovan said: Researchers must avoid harming the birds during capture to fit them with the devices and during recapture to get the data. Straps on the packs can cause irritation, and the environment can always present hazards.
“There’s always a small percent of damage or mortality due to the effort itself, which is unfortunate. The hardest thing is we’re concerned about individuals but we’re worried about populations,” Donovan said.
The research will gather information needed to give conservation efforts more insight into the full lifecycle and habits of this rare bird, he said.
Lindsay Dunbar reports for Great Lakes Echo.