The species that spurred the first Global ReLeaf forest has come a long way in the last 20 years.

By Gary Lantz

The AuSable River runs through Michigan, supporting a vital jack pine watershed, as well as a great place for warbler-spotting tours. (Credit: Dennis Cox/Worldviews)

In this era of diminishing forests, declining species, and concern over climate change, those doing the often-thankless work on behalf of the natural world seldom have something substantial to cheer about. But during the last decade or so, a tiny summer resident in Michigan’s jack-pine country has given the conservation community a reason to smile. A consortium of state and federal agencies, conservation organizations, and private citizens has shown that a small bird can inspire a huge effort, and that a species once doomed to extinction can flourish because people care.

The brashly singing, beautifully plumaged Kirtland’s Warbler is five-plus inches of unabashed energy cloaked in gray, black, brown, and bright yellow. Weighing in at approximately half an ounce, the bird journeys from its winter home in the Bahamas to nest in a very specific part of Michigan’s north woods.

If the warbler’s exacting nesting requirements aren’t met, it doesn’t do a very successful job of reproducing. Scientists believe that because of its finicky tastes, the warbler never was a particularly numerous species. And when human settlement and commercial timber harvest altered natural forest cycles, the Kirtland’s numbers plummeted.

The key to successful Kirtland’s nesting is jackpine forest growing on the sandy soils this tree prefers. Another key ingredient is site disturbance that produces a mosaic of tree age classes. Kirtland’s warblers require young jack pines for nesting cover. Before human settlement, such cover was a naturally occurring pattern wrought by periodic wildfire.

A singing Kirtland's warbler. (Credit: Ron Austing)

Historically, jack-pine forest in both upper and lower Michigan was constantly renewed by naturally occurring blazes. Fire resulted in open space among the jack-pine islands, accelerated the growth of brushy, grassy groundcovers, and, most importantly for the warblers, created a mosaic of young pines in successive stages.

Kirtland’s warblers begin to nest under jack-pine stands when the young trees reach five feet tall, or around five to eight years of age. The birds continue to use this nesting habitat until the lower limbs begin to die back, when the tree reaches 16 to 20 feet, or about 16 to 20 years of age.

These ground-nesting warblers like their jackpine islands to encompass more than 80 acres, and the nesting territory of each pair may range anywhere from 1.5 up to 10 acres. In their reproductive desires, Kirtland’s are also picky about soil type. Almost all Kirtland’s warbler nests can be found on Grayling sand, a soil base that supports the plant communities the birds prefer.

Twentieth-century fire suppression, along with modern timber-management practices, reduced disturbance in Michigan’s jack-pine stands, and Kirtland’s warbler numbers plummeted dramatically due to reduced nesting habitat. The bird was granted endangered species status in 1967.

Biologists believed that the only way to save the warbler was restoration of adequate nesting habitat. The U.S. Forest Service and the Michigan Department of Natural Resources began manipulating federal and state jack-pine forests to provide for the successive growth the birds required, and by 1973 these revitalized areas contained more than half of the remaining nesting population.

The successful renewal of reproductive patterns encouraged even more strategic jack-pine logging, burning, seeding, and replanting…the kinds of disturbances that provide the thick stand of young trees the birds seek for nesting. By the 1990s Michigan could boast of more than 150, 000 acres of jack-pine forest specifically managed for Kirtland’s warbler recovery.

While warbler numbers steadily increased, the jack-pine stands also provided habitat for upland sandpipers, eastern bluebirds, white-tailed deer, black bears, snowshoe hares, and several rare plants that occur only in fire-disturbed jack-pine clearings.

As all this was going on, biologists were removing another threat to the fragile Kirtland’s warbler population. Brown-headed cowbirds, once native to the buffalo plains, extended their range with the introduction of the domestic cow and the plow. Cowbirds once followed the rambling bison herds, gleaning insects stirred up by, or attracted to, large aggregations of grazers. And because the herds were continually on the move, cowbirds evolved a strategy of nest parasitism, laying eggs in any available nest, moving on with the buffalo, and letting foster parents hatch and raise the cowbird chicks.

When the buffalo disappeared, cowbirds turned to the company of domestic cattle grazing amid cleared homesteads in former woodland east of the Great Plains. They began to parasitize eastern woodland songbird nests, and, although the cowbirds were only doing what came naturally, their intrusive ways took a toll on Kirtland’s warblers.

The speckled egg is that of a Brown-headed cowbird, laid alongside those of an Eastern Phoebe. This nest piracy prevents Kirtland’s warblers from successfully raising their own young. (Credit: Gala Webdesign)

Cowbird eggs are bigger than many of the eggs in nests they “borrow.” These eggs tend to hatch before those of the host, and the chicks are aggressive and out compete warbler hatchlings. Many songbird species with stable populations are able to absorb cowbird parasitism, but with Kirtland’s numbers on the cusp, biologists decided to trap and remove as many cowbirds as possible. As a result, nesting success rose sharply.

More than anything else, stabilization and rejuvenation of Kirtland’s warbler populations has been a product of innovative forestry techniques, all of them centered around the jack pine (Pinus banksiana). Jack pine is a tree closely related to lodgepole pine, and the two species hybridize wherever their ranges overlap.

Jack-pine needles are two to a bundle, and measure three-quarters of an inch to two inches long. The trees may grow to an average of 55 to 65 feet tall at maturity, though some have been known to reach 100 feet in height while measuring 25 inches in diameter. Jack pines can live 200 years or more, but many begin to show signs of decay much earlier.

This tree of both the northcentral and northeastern U.S. and Canada can be found on boreal forest burns, dry hills, sandy dunes, rock outcrops, rocky ridges, and lake shores. Those growing on sandy soil often are small and bushy. Jack pine is the best-adapted to fire of all the northern conifers. Populations can quickly reestablish in the wake of a forest fire due to the species’ serotinous cones, or cones coated with a resin that must be melted by fire before opening and releasing the seeds within. Seedlings grow quickly in full sunlight, and within five or six years are thick, tall, and bushy enough for nesting Kirtland’s warblers.

Today, thanks to a sound recovery plan by federal and state officials, and ample assistance from individuals and private organizations, jack-pine stands and Kirtland’s warblers are once more surviving in sync, with swelling numbers to show for it.

When the initial recovery goal was established in the 1970s, endangered- species biologists hoped someday to count 1,000 male warblers singing on nesting territories. Recently this number was exceeded for the seventh year in a row, and as many as 1,697 calling males, each indicative of a mated, nesting pair, have been recorded—a huge gain over the 1987 count of only 167.

Biologists expect to monitor populations for several more years, and then, if the current successful trend continues, they’ll conclude that the diminutive visitor from the tropics can be counted as a major conservation success story. At the same time, however, they caution that the bird will always be management-dependent, and if conservation efforts decline, so will the bird.

Jack pine barrens, the Kirtland's warbler habitat of choice. (Credit: Paul Bolstad, University of Minnesota, Bugwood.org)

“When you talk about the Kirtland’s warbler, you have to understand that it’s a conservation-reliant species that needs to be managed into perpetuity,” pointed out Paul Thompson, a U.S. Forest Service wildlife biologist. “We can’t just walk away.” This means the continued planting, culling, cutting, and burning of jack-pine forest, plus the funding to keep the program alive and consistent.

Since federal wildlife recovery funds have been lean of late, conservationists hope to establish an endowment to provide for future habitat management. Currently, a national forest in Michigan spends an average of $350 an acre each year to maintain the Kirtland’s warbler habitat it oversees. Of the 150, 000 acres in state and federal forestland set aside for the warblers, some 38,000 acres must be managed annually on a rotating basis to provide adequate nesting habitat.

The use of both fire and clearcutting to produce warbler habitat has met with some public opposition. However, the negatives have been somewhat offset by nature tourism, especially by birders who flock to see the rare winged visitor from the south. At the same time, rapid replanting and recovery of clearcuts haves produced positive public relations for the Kirtland’s recovery team.

Education and public outreach have been another cornerstone of the recovery effort, and one of the programs, a popular wildlife festival, is lauded as among the best of its kind in the nation. The Kirtland’s Warbler Wildlife Festival, held on the campus of Kirtland Community College, Roscommon, Michigan, offers visitors an opportunity to see firsthand both Kirtland’s warblers and the continuing efforts to provide prime habitat for them. The warbler recovery team— including representatives from the Michigan Department of Natural Resources, the U.S. Forest Service, U.S. Fish & Wildlife Service, U.S. Geological Survey, Patuxent Wildlife Research Center, Canadian Wildlife Service, University of Toronto Earth Sciences Center, International Institute of Tropical Forestry, the Nature Conservancy, and the Bahamas Department of Agriculture—meet annually on the campus of the appropriately named institution to discuss ongoing recovery efforts.

The 2010 festival is scheduled to begin May 15 on the Kirtland campus. No preregistration is required; however, a $5 Kirtland’s Warbler Wildlife Festival Button will be needed by anyone 15 years old or older who wishes to attend a variety of presentations and guided bus tours.

The festival—sponsored by Kirtland Community College, the Michigan Department of Natural Resources, the U.S. Forest Service, and the U.S. Fish & Wildlife Service—features Kirtland’s warbler tours, nature walks, an art show, arts and crafts displays, rock hunts, area birding tours, and presentations on a variety of regional wildlife including sturgeon, trumpeter swans, warblers, insects, raptors, bats and bat houses, silk moths, native wild cats, an eagle update, plus live music and plenty of food for everyone.

Kirtland’s warbler management areas include 119 sites scattered across eight counties. The U.S. Fish and Wildlife Service, the U.S. Forest Service, and Michigan Audubon Society host tours for birders beginning May 15 and extending through July 4. Officials point out that these tours, or those provided through the wildlife festival, remain the best way to see this endangered species.

Forest Service tours depart the Ramada Inn in Grayling, Michigan at 7 a.m. and are offered free of charge. U.S. Fish and Wildlife Service tours require a fee of $10. Officials stress that actual Kirtland’s warbler sightings can’t be guaranteed. Prime viewing is late May through June. Information is available at http://www.fs.fed.us/r9/hmmf/pages/warbindex.htm.

The Kirtland’s Warbler restoration story wouldn’t be complete without mentioning the private conservation organizations that came on board at the onset and continued to work, contribute, and never lose faith through decades of trial-and-error effort.

One of these organizations, American Forests, completed its first Global Releaf forest planting 20 years ago in Michigan. The trees were jack-pine seedlings, and they went into the ground as part of the overall effort to save the Kirtland’s warbler. American Forests has been instrumental in jack-pine regeneration since that date, partnering with both public and private interests to insure the long-term stability of this, one of the rarest of rare birds.

Over the years, American Forests has set the standard for forest renewal in the nonprofit sector. By the spring of 2010 the organization had sponsored the planting of more than 30 million trees as part of more than 600 projects during a highly productive 20-year period. Their goal is to plant 100 million trees by the year 2020 by planting twice as many trees in half the time.

American Forests officials will be on hand at this year’s Kirtland’s Festival, both to celebrate a resounding success story and to announce the Global ReLeaf projects planned for 2010. There they’ll join biologists, foresters, wildlife ecologists, project sponsors, and bird lovers fromaround the world, all gathered to toast an amazing comeback by a tiny battler that’s still in the game—thanks to an admirable amalgamation of caring hearts and helping hands.

— Gary Lantz writes from Norman, Oklahoma

This article was published in the Spring 2010 issue of American Forests magazine.