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2012 is a Banner Year for Kirtland’s Warblers
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“It was only 1987 when we tied an all-time low of 167 singing males. This is a pretty remarkable recovery -- 12 times the population size from where it was just a short 25 years ago,” said Scott Hicks, the Service’s East Lansing Field Office Supervisor.
Biologists, researchers and volunteers in Michigan observed 2,063 singing males during the official 2012 survey period – up from 1,805 in 2011. In Wisconsin, a minimum of 23 singing males were observed in five counties. Another four males were counted in Ontario.
In Wisconsin, volunteers and paid monitors found and tracked singing male Kirtland’s warbler and were able to monitor nesting. Kirtland’s warblers were recorded in five counties in Wisconsin (Adams, Douglas, Bayfield, Vilas, and Marinette), and at least 24 singing males were verified. Due to the necessity of taking a cautious approach to monitoring nests, there is limited information on nesting outcomes. However, 14 nests that ultimately fledged 8 to 13 young were documented. One concern regarding nest monitoring is the potential to lead predators to the nests. This year use of digital video recording to monitor nests was tested and may be a useful alternative. We are learning a lot as we watch a species expand its range by pioneering into new areas in Wisconsin.
The Kirtland's warbler survey is conducted during the second and third weeks of June, when the birds are defending their nesting territories. Warblers are detected by listening for their songs, which can be heard at distances up to one-quarter mile. 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.
Kirtland’s warblers typically nest on the ground 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. Modern fire suppression programs altered this natural process, reducing Kirtland's warbler habitat. As a result, the population of Kirtland's warblers declined to the point that they were listed as endangered.
To mimic the effects of wildfire and ensure the future of this species, the DNR, the U.S. Forest Service and the U.S. Fish and Wildlife Service manage the forests through a combination of timber harvests, burning, seeding and replanting to promote habitat for many species, including snowshoe hare, white-tailed deer, other songbird species and rare plants.
Michigan Kirtland’s Warbler Tours Attract Growing Number of Birders
Each year, in late spring and early summer, birders from around the globe trek to northern Lower Michigan to see Kirtland’s warblers. This year, a total of 687 tourists took advantage of guided tours, an 18 percent increase from last year's number and comes after a 47 percent increase in attendance in 2011. The jump occurred even though tours were scaled back this year.
Tourists came from 37 of 50 states, Puerto Rico and five foreign countries. Participation by visitors from California, Illinois, Michigan, Ohio and Pennsylvania was significantly higher in 2012 compared with the average from the past eight years. The increase in Michigan participation was most noticeable, reflecting the effort to reach out to Michigan media outlets and inform Michigan residents of the world-famous resource in their own state.
New Methods will Help Track Migrating Kirtland’s Warblers
As the month of October began, the last few Kirtland’s warblers that remained on the breeding grounds in northern Michigan finally departed. They have embarked on a journey spanning more than 1,600 miles. Many will likely pause enroute somewhere between Michigan and the Bahamas to rest and refuel before finally arriving at their winter home. The vast majority of these individuals will go undetected as they fly south, eluding the eyes of ever-watchful birders as they have done since the species was first discovered in 1851. A small sample of this population, however, promises to remove some of the obscurity associated with this species during the non-breeding season and literally shed light on where these birds spend the bulk of their time outside of Michigan.
In the spring of 2012, the East Lansing Field Office began a project in collaboration with Dr. Pete Marra of the Smithsonian Institute to track the movement of Kirtland’s warblers from their breeding grounds to their winter grounds. Several Kirtland’s warblers were equipped with light-level geolocators during the 2012 breeding season. These devices are incredibly small, weighing just 0.65 g, and will record time and light intensity levels while the individual wears the device. Upon re-capture of these birds next spring, data archived on the device will be downloaded and analyzed to determine where those individuals have been (accuracy is approximately ± 200km). This information will help clarify the geographic distribution of the species during migration and winter seasons. It will also facilitate future studies that examine the biology and ecology of the Kirtland’s warbler during these important periods of its annual life cycle. Most importantly, this new information will increase our ability to identify and ensure that threats to the survival of this endangered species are adequately addressed across the entirety of its range.
Students Get Up-Close Look at Kirtland’s Warblers
Getting kids excited about wildlife is always a goal for the Service, and the East Lansing Field Office launched an effort to show local third-graders the amazing resource right outside their doors. In late May and early June of 2012, biologists from the East Lansing Field Office travelled to elementary schools in northern Lower Michigan to educate approximately 365 third graders about the Kirtland’s warbler. Biologists visited classrooms to introduce students to endangered species and the plight of the Kirtland’s warbler through an interactive presentation and educational game. Students learned to identify a Kirtland’s warbler by sight and sound, learned about the special type of jack pine habitat the species needs during the breeding season, and how the surrounding area, where the students live, is also used by hundreds of Kirtland’s warblers. Biologists also introduced students to the brown-headed cowbird, the concept of nest parasitism, and the impacts the cowbird has on the Kirtland’s warbler populations. Kids participated in a cowbird game, in which students played the roles of warbler or cowbird during a mock breeding season.
Biologists later took students on walking field trips of nearby jack pine forest stands to see first-hand Kirtland’s warbler nesting habitat and management efforts that benefit the species. Students practiced identifying Kirtland’s warblers and other birds by sight and sound, while using binoculars and spotting scopes. During these field trips, biologists explained why large stands of young jack pine forest are important to Kirtland’s warblers and why fire is critical to the regeneration of this habitat type. Students were then asked to discuss some of the challenges that humans experience living in a fire-prone environment, and learned how land managers are able to artificially regenerate Kirtland’s warbler nesting habitat in the absence of wild fires, so that humans and Kirtland’s warblers can successfully co-exist.
After a tour of the nesting habitat, students learned about migration and the Kirtland’s warbler annual cycle through a game in which students had to “migrate” to their winter grounds and back. In addition to avoiding the common hazards of migration, such as poor weather and predation, students also had to respond to human-caused changes to habitat (both positive and negative). In this way, students were better able to understand how the breeding, migratory and winter phases of the species were connected, and how events happening in one place at one time were linked across the species’ annual cycle, to the survival of individual birds, and to population trends.
The education program will continue on an annual basis, in order to build a more educated public, whose lives intersect most directly with that of the Kirtland’s warbler.