Warblers on the rise

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MARQUETTE - The number of Kirtland's warblers is continuing to rise in the Upper Peninsula and across Michigan, according to surveys of the endangered species completed in June.

"We're up slightly in the Upper Peninsula," said Christie Deloria-Sheffield, a biologist with the U.S. Fish and Wildlife Service in Marquette. "It's the highest number we've ever recorded in the U.P. since we've been doing it."

There were 34 male Kirtland's warblers found across five U.P. counties, up two from last year. Of these, there were six found in Marquette County, including one on the Yellow Dog Plains.

Five were found in Schoolcraft County, one in Luce County, 10 in Delta County and 12 in Chippewa County, including some in the Raco area where Hiawatha National Forest habitat improvement efforts for the species have been ongoing.

The survey in the U.P. was conducted June 6-15 under some poor weather conditions including rain, cold and wind. Deloria said this factor may have delayed the return of some of the birds to the area.

Census takers in the U.P. were part of a multi-agency effort including the U.S. Fish and Wildlife Service, U.S. Forest Service, the Michigan Department of Natural Resources and a number of volunteers.

Statewide, Kirtland's warbler singing male numbers reached 1,792, up from 1,697 last summer and 1,478 in 2006. The new high is the record number recorded in Michigan since the surveys began in 1951.

The lowest numbers were recorded in 1974 and 1987, when only 167 singing males were found.

During the surveys, warblers are detected by listening for their songs. The songs can be heard at distances up to mile, providing an excellent way to detect the birds with minimum disturbance.

Only the males sing, so estimates of breeding population size are obtained by doubling the number of singing males recorded, based on the assumption that each male has a mate in its territory.

Although Kirtland's warblers have begun to expand into new areas, including the U.P., Wisconsin and Ontario, the core of the Kirtland's warbler population remains dependent on northern Michigan's jack pine barrens ecosystem for nesting habitat.

The warblers nest on the ground and typically select nesting sites in stands of jack pine between four and 20 years old. Historically, these stands of young jack pine were created by natural wildfires that frequently swept through northern Michigan.

Modern fire suppression programs altered this natural process, reducing Kirtland's warbler habitat. The result was that the population of Kirtland's warblers declined to the point that they were listed as endangered species.

To mimic the effects of wildfire and ensure the future of this species, the DNR and its partners at the state and federal level manage the forests through a combination of clearcutting, burning, seeding and replanting to promote warbler habitat.

Approximately 3,000 acres of jack pine trees are planted or seeded annually on state and federal lands, primarily for the purpose of providing habitat for Kirtland's warblers.