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Kirtland Warbler: Prescribed Burns May Help
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JULY 29, 2004 --Research at Michigan Technological University could prompt the rare Kirtland's warbler to make a home on the Baraga Plains.
In an effort to regenerate jack pine habitat, several one-acre, clear-cut plots were set ablaze south of Camp Alberta July 22. The Michigan Department of Natural Resources conducted the prescribed burn on Michigan Tech land under gray skies in drizzling rain. Despite the dampness, the pitch-rich, pine debris burned fast and hot, a prerequisite for jack pine regeneration.
"Jack pine is a fire-adapted species," said lead researcher Andrew Storer, an assistant professor in the School of Forest Resources and Environmental Science. "Its cones often stay closed until there's enough heat to open them and release the seeds."
There's plenty of jack pine on the Baraga Plains, but that's not enough to attract the Kirtland's warbler for more than a visit. The showy, blue and yellow birds nest only in jack pine forests of a certain age, about five through 10 years old.
Storer's team will study plots treated in three different ways and see what sort of forest results. In addition to the fire-treated plots, researchers are studying areas that are disrupted by dragging chains over the soil, and plots that have been both disrupted and burned.
"Kirtlands need a high density of young trees, and we are anticipating that at least one of these treatments will create that density," Storer said.
Kirtlands have been spotted in the area, but just in passing. Lacking proper habitat, they haven't stayed to nest.
In the meantime, Storer's team will see how other forest creatures respond to the new habitats. "If we do produce that density, how will it affect other organisms?" he said. "We'll be looking at insects and other species that use the forest floor, particularly predatory ground beetles, ants and spiders. It may be that by creating dense forests, we could hurt some species that prefer an open woodland."
The Kirtland's warbler could be considered a poster child for the success of the Endangered Species Act, says ornithologist David Flaspohler, an associate professor in MTU's School of Forest Resources and Environmental Science. "If was one of the first species listed under the act," he said. "They've done well as a direct result of human management, including habitat restoration and the control of the brown-headed cowbird in their habitat."
Cowbirds lay their eggs in warbler nests. Hatching before the warblers, the cowbird young get fed first, grow quickly and often outcompete the warbler chicks for food. This can cause massive reproductive failure, which for the short-lived Kirtland's warbler, with its two- to three-year life span, can cause rapid declines in the entire population.
"Without management, Kirtland's warblers might have disappeared," Flaspohler said. "They need a jack pine forest that's not too young and not too old; they are ultra-specialists, more so than any other species of warbler. Even in pre-European settlement times, they probably were not all that common."
Some have suggested that the Kirtland's warbler, which nests only in eight Lower Michigan counties, be honored as the state bird. It would replace the robin, which is found throughout North America. "Thousands of people don't come to Michigan to see robins, but they do to see Kirtland's warblers. It's a very special bird," Flaspohler noted.
The one-acre test plots near Camp Alberta aren't big enough to support a breeding population of warblers, but they could determine whether or not its possible to create warbler habitat on the Baraga Plains.
"If we can achieve that kind of density in a jack pine forest--and if there's the political will to establish a second population of warblers--these tools could be used over a larger area," Storer said.
CONTACTS: For information on the research program, contact Andrew Storer, storer@mtu.edu, 487-3470. For information on Kirtland's warblers, contact David Flaspohler, djflaspo@mtu.edu, 487-3608
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