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What a songbird sings

August 2, 2011


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A golden-winged warbler with an identity color band.

could tell the world a lot about our environment.

By Adam Overland

You may have noticed, if you’ve ever left your windows open on a cool Minnesota evening, that birds wake up early, busy with the work of chirping even before sunrise, and far before the human economy starts humming. U professor John Loegering and U postdoc Henry Streby are up early, too. They’re both part of the Golden-winged Warbler Working Group (GWWA), a consortium of researchers across the country working to learn more about the species.

One in six Americans identify themselves as birdwatchers, according to a 2009 U.S. Fish and Wildlife Service (FWS) report; but few are likely to have had the chance to see the golden-winged warbler outside of a photograph. The birds are elusive creatures; tiny, and few in number. The question is, how few, where, and why?

In February of 2010, a law student at an east coast university submitted a request to the FWS to list the golden-winged warbler, a bird maybe four inches long and weighing less than half an ounce, on the Federal Endangered Species List. After officially taking up the case in early June, the FWS has 90 days to determine whether to put the little bird on the list. The 90-day finding will be the first step in a process that triggers a review of the best biological information available. And it turns out, the best information available is being discovered, right now, right here, at the U.

The golden-winged warbler has been declining on the east coast at a rate of 6 to 7 percent per year for some 40 years. In Connecticut, they’re declining 23 percent per year. “At that rate, you can see it doesn’t take very long before you have a problem,” says Loegering. The golden-winged warbler, in fact, is already listed as either endangered or threatened in most of the states where they’re found, says Streby. Not so in Minnesota.

Laying the groundwork

John Loegering, who spends half of his joint-appointment as an Extension Wildlife Specialist  on the St. Paul campus, began his work 4 to 5 years ago, research which the UMC professor describes as getting the ball rolling. His home-base location at the U’s Crookston campus turns out to be ideal, since many of the birds nest in the Tamarac National Wildlife Refuge, not far southeast of UMC. Loegering says his early research goals were simple—basic occupancy and reproduction habits. “They knew virtually nothing about golden-wings in Minnesota when I started,” says Loegering. “But Henry put together a proposal looking at a much broader geographic range in the region…much more complicated with a more thorough research design.”

Streby, advised by David Andersen of the Minnesota Cooperative Fish and Wildlife Research Unit, and working with U graduate student Sean Peterson, says Loegering’s earlier work showed that what was really needed was a much more intensive study in the core of the range; a demographic study focusing on where the birds are actually doing well.

Minnesota, land of 200,000 golden-winged warblers 

There are an estimated 200 to 400 billion birds on this planet. Of those, just about 400,000 are golden-winged warblers (this estimate, in fact, recently grew from 200,000 to 417,000 as a result of GWWA work). Fully two-thirds are found either here in Minnesota, in the other study site in southern Manitoba, or in nearby Wisconsin. Nearly half of the population summers in Minnesota. “No other bird species is so concentrated in Minnesota,” says Loegering.

Want to see more?

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View a photo album of the golden-winged warbler and the research team at U of M Facebook.

The warbler winters in Central and South America, as do so many other bird species, causing the competition for food to become so fierce that the warbler takes to the skies during the most precious months of its life cycle—breeding season. And of all the places in the world to choose from, the four-inch bird flies thousands of miles to nest in greatest density here in Minnesota.

Streby’s project uses telemetry—miniature radio transmitters harnessed on a warbler’s back—to track their movements. But to attach a radio transmitter, one must first catch a small, delicate creature that flies. And that isn’t easy.

The work begins in May, about a half an hour before sunrise, with the researchers stringing large, fine mesh nets that won’t injure the birds, says Streby. Once caught, researchers place a transmitter, weighing less than half a gram, on the bird’s back. While they still search for the birds the old-fashioned way—“roaming around with a stick, tapping the ground, hoping to flush out a bird,” says Streby, “putting transmitters on them…is turning out to be really the only way to track them to their nests.” Stick tapping, says Streby, results in about one nest found per 30-person hours of searching. “Nests are incredibly difficult to find. They’re on the ground, and they’re basically a tiny bowl of leaves, which looks like every other clump of leaves on the ground, in dense vegetation. It’s a needle in a haystack.” 

Time to update the Wikipedia entry

The fact that the birds are so hard to find may itself have contributed to the slow advance of knowledge about the golden-winged warbler. Scientists would search in proven areas where the birds had been found before. It’s comparable to belief-bias, in which people tend to accept things that fit with what they think they know. “Previous knowledge only told you where to look for a nest; and so you look there, and sure enough, you find them where people found them before,” says Streby.

The perils of research

During his research, Henry Streby has been given lodging at an old field house in the Tamarac National Wildlife Refuge, one with holes in the walls, he says—and no absence of mosquitos.

He's spent the past weeks tearing through the dense vegetation with a receiver and an antenna in hand, figuring out where the golden-winged warbler goes. In the process, he's been attacked by mosquitos. "We coat ourselves in 40 percent DEET pretty regularly, and I have been on the verge of going insane with some of the days of mosquitos this summer," he says. He recalls a time when he had so many mosquito bites he began to have an allergic reaction. "I had to run to the truck and turn on the air-conditioning. My skin was on fire."

Ticks are a problem, too—members of both Streby and Loegering's staff have come down with Lyme disease this summer and in years past.

"There usually comes a point in July when I start to miss the cool, air-conditioned office...that's after about two months in the field. But it usually takes two to three hours after I'm back in the office before I wish was back out in the field. Every moment in the field I'm complaining—but I love it. My mom is still amazed that I found a way to get paid to run around in the woods," says Streby.

So, any regurgitation of the best available information will tell you golden-winged warblers prefer to nest in early successional areas (very young forest), or right along the edge of mature forests. Not necessarily so, says Streby.

“This is the only project to put radio transmitters on these birds, and to let them tell us where their nests are. Every day we track a bird we find out something that nobody knew,” says Streby.

“What we now know is that the Tamarac National Wildlife refuge is exactly right for golden-winged warblers. It’s very dynamic, it’s got every habitat range from recently clear-cut areas, to burned areas, to relatively untouched mature forests, and shrubby wetlands, and that seems to be ideal for golden-winged warblers—and they use almost all of it, throughout the summer,” says Streby. “They need everything.”

That’s a key insight into the problem of the warbler’s decline in the east. “We’ve tried for so long now to keep any cuttings or fire or anything from disturbing a forest, except human development. So you either have mature forests, or you have people. And golden-winged warblers need more than the mature forests, and less of the people. To have one part of it, or none of it, is what won’t work for them.” As it turns out, Northern Minnesota has it all.

“This is something that could be a source of pride that no one knows about. I mean, we all know that Minnesota has a lot of loons…but I would venture to guess that most Minnesotans have no idea what a golden-winged warbler is or looks like, and you’ve got half of the world’s population breeding in Minnesota. The reason they’re here is because Minnesota manages its forests pretty efficiently. It’s something Minnesota is doing right.”

As the FWS concludes its 90-day finding, it will be looking at the research conducted here, and in Minnesota’s forests. And it will find that this little bird is doing alright in Minnesota says Streby. 

The value of a chirp 

If the golden-winged warbler has a message for us, it may be one of diversity. What is the definition of a forest? Streby argues that it’s one that changes. And the creatures that live within them can help us expand on that definition. “When humans move into a system, we tend to arrest change, and we say, “this is a forest—a big, old mature forest is a real forest.”

Loegering agrees. “What we may want a forest to be is just one component of a dynamic system—one that was dynamic in the past. It’s just dynamic on a very slow timescale that humans don’t perceive,” he says.

Ultimately, of course, this is about more than a small bird. It is about habitat management on a much broader scale. It’s about hard questions, like whether we let a forest burn, and to what extent, and whether we allow logging, and to what extent. To answer questions environmentalists, politicians, and well-meaning people the world over have debated and continue to debate, we may only need to listen to a tiny bird. “They’re not the loudest bird, they don’t have the sexiest song in the forest,” says Streby. But they have something to say all the same.

Tags: College of Food, Agricultural and Natural Resource Sciences, Extension

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audioBaby golden-winged warblers begging for food