USA — Clare Countys population of the rare and endangered Kirtlands Warbler seems to be down from previous years, but overall the population appears to have stabilized and even grown, according to a report released Monday by the Michigan Department of Natural Resources.
Researchers detected 1,805 singing males across the birds range during the survey period in June. Thats an increase from 2010, when a revised total of 1,747 males were observed.
The biologists, researchers and volunteers found 84 singing males in Clare County this year. Thats down from last years total of 99 discovered in northern and western Clare County near Temple and Leota.
The first birds were spotted there nine years ago, and as recently as 2007, researchers tracked 147 singing males in that area. But as the habitat has changed, so has the population. The elusive bird is extremely sensitive to habitat changes, according to experts on endangered species.
The warblers nest on the ground and typically select nesting sites in stands of jack pine between 4 and 20 years old. Historically, these stands of young jack pine were created by natural wildfires that frequently swept through northern Michigan, the DNR said.
Modern fire suppression programs altered this natural process, reducing Kirtlands warbler habitat. The result was that the population of Kirtlands warblers declined to the point that they were listed as endangered.
As late as 1987, only 167 singing males were recorded.
To mimic the effects of wildfire and ensure the future of this species, the DNR, the U.S. Forest Service, and U.S. Fish and Wildlife Service manage the forests through a combination of clearcutting, burning, seeding and replanting to promote habitat for many species, including snowshoe hare, other warbler species, and rare plants. Because large prescribed fires can easily get out of control in northern Michigans woodlands, about 3,000 acres of jack pine trees are harvested and replanted annually on state and federal lands.
The Kirtlands warbler habitat program is successful because there are many benefits, said Keith Kintigh, DNR wildlife ecologist. Not only are we providing habitat for an endangered species, we are also providing wood products and great hunting opportunities for snowshoe hare, deer and turkey, to name a few.
The largest numbers of birds again were found this year in the jack pine barrens of Ogemaw County, near West Branch. Others were found in Alcona, Crawford, Iosco, Kalkaska, Montmorency, Oscoda, Otsego, Presque Isle and Roscommon counties.
Bird also were tracked in seven Upper Peninsula counties, where 35 singing males were discovered. Another 21 were located in northern Wisconsin, and two pairs in Ontario.
The Kirtlands warbler survey is conducted each year during the second and third weeks of June when the birds are defending their nesting territories. Warblers are detected by listening for their songs.
The songs can be heard at distances up to one-quarter 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.
State biologists said the population has not increased or decreased by more than 5 percent since 2007. The bird was one of the first animals placed on the endangered species list in 1973, and it has remained there ever since.