Forest Service census reveals healthy Kirtland’s warbler population

A male Kirtland’s warbler warbles. (Courtesy photo/Sawyer Frederick)

MIO — One of America’s greatest conservation success stories continued this summer with the Huron-Manistee National Forests’ 2019 Kirtland’s warbler census.

Earlier this summer, Forest Service staff, partners and volunteers counted 1,023 singing male warblers in Michigan’s Huron National Forest, marking the third consecutive census in which more than 1,000 singing males were identified. The tally represents more than 40 percent of the total population of male Kirtland’s warblers.

“The count was down slightly from 2017, but that may have been because of the rain,” said Huron-Manistee National Forests Biologist Phil Huber. “Overall, the figure indicates a healthy population.”

Thirty years ago, the Kirtland’s warbler was on the brink of extinction. Human efforts to suppress wildfires resulted in substantial habitat loss; the warbler nests exclusively in young jack pine forests that require fire to regenerate. Meanwhile, warbler nests were ravaged by the brown-headed cowbird, a brood parasite that manipulates other species into rearing its young at the expense of their own.

In response, the Forest Service, the U.S. Fish and Wildlife Service, the Michigan Department of Natural Resources and other partners formed the Kirtland’s Warbler Recovery Team. Since rebranded as a “conservation team,” the group has been so successful that the Kirtland’s warbler is under consideration for removal from the federal endangered species list.

“Every species is important,” said Mio District Wildlife Biologist Kim Piccolo. “The conservation team is setting up a model for other conservation-reliant species.”

The Kirtland’s warbler nests almost exclusively in the young jack pine forests of northern Michigan. (Courtesy photo/Sawyer Frederick)

The Kirtland’s warbler census is an integral part of the conservation team’s efforts. Initiated in 1951, the census was conducted annually each June between 1971 and 2017, when it was moved to a biennial schedule.

At the beginning of each census, the Forest Service draws parallel lines called transects at quarter-mile intervals throughout Kirtland’s warbler nesting habitat. Each census taker walks at least two miles of transects per day. This year’s census takers covered more than 23,000 acres over an eight-day period.

Weighing just half an ounce, the steel blue and yellow Kirtland’s warbler can be difficult to spot, even for experienced birders. Census takers therefore stop for five minutes every 200 hundred meters to listen for the warbler’s distinct song.

Upon hearing a warbler, census takers use a compass bearing to plot the bird’s probable location on a map. Census takers compare their results at the end of each day to eliminate duplicates.

Though labor-intensive, these methods ensure a high degree of accuracy. The Forest Service can afford to employ such methods thanks to a group of dedicated volunteers who arise well before dawn on census days to count singing warblers.

“You get up very, very early,” said Karen Markey, a census volunteer for 18 years. “It’s exhausting, don’t get me wrong, but I enjoy nature and giving back.”

Huber and Piccolo encourage new volunteers, particularly those with birding or orienteering experience. Prospective volunteers should be capable of walking several miles over rough terrain and must be prepared to contribute to census efforts for a minimum of five years.

Guided tours of Kirtland’s warbler habitat are a less intensive way to get involved. The Mio Ranger District offers such tours annually between May 15 and 31. More information can be obtained at www.fs.usda.gov/hmnf or by emailing SM.FS.MioKWTours@usda.gov.

“Just spreading the word and teaching others about the Kirtland’s warbler is really important,” said Piccolo. “There is value in not losing parts of our forest.”

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