 |
||
 |
 |
|
 |
 |
|
|
Featured Research Project (April - May 2003) Landscape Ecosystems and the Recovery of the Wayne S. Walker and Burton V. Barnes, SNRE Introduction Focusing on spaces as well as species, the landscape ecosystem approach provides the basis for conserving rare and endangered species by understanding the landscapes that sustain them.
Declining Numbers of Warblers Warbler populations were maintained for centuries by wildfire which periodically created the young pine-oak stands. However, the population declined from an estimated 500 breeding pairs in 1961 to about 200 in 1972, primarily as a result of habitat loss. Forest fragmentation and fire suppression are the primary causes of lack of habitat. Due to the decline in the warbler population, the Kirtland's Warbler Recovery Team was established in 1975. The recovery plan formulated by this group called for developing and maintaining 36,000 to 40,000 acres of suitable nesting habitat either by regenerating jack pine by prescribed burning or planting.
Mack Lake Burn
Results After the 1980 burn, the growth of pines and oaks followed the landform-based patterns of microclimate and soil - relatively fast in the high-elevation landforms and comparatively slow in the low-elevation landforms surrounding Mack Lake. As a result, jack pine trees reached acceptable height (ca. 1.5 meters) for warbler colonization in the high-elevation landforms sooner than in the low-elevation landforms.
As seen in the map in Figure 1, the progression of warbler colonization (note spatial position of population mean) from 1986 to 1997 followed the high-to-low landscape ecosystem pattern. As seen in Figure 2's chart, in 1986 and 1987, the bulk of the Mack Lake warbler population occupied the high-elevation landforms where site conditions were most favorable for nesting. Gradually, as the slower-growing jack pine trees of the low-elevation landforms reached acceptable height, warbler colonization shifted to these increasingly favorable sites. The decline of the warbler population in the high-elevation landforms occurred when the pines grew larger, and their lower branches died back.
As a result, nesting habitat under the trees became exposed and therefore unfavorable for this ground-nesting bird. Once the warblers saturated the Mack Lake burn, the "overflow" birds colonized new areas, often plantations, in areas outside of the burn. Because of the unique two-leveled topography and concomitant high ecosystem diversity, the Mack Lake burn supported warbler populations far longer (ca. 15 years) than would have been expected in a less diverse landscape. Thus, the distinctive landscape of the Mack Lake basin provided a virtual "lifeboat" for declining warbler populations and acted as a springboard for the high numbers of birds (1,050 breeding pairs in 2002) now achieved through ecosystem management.
The Kirtland's warbler is an inseparable part of landscapes where physiography, microclimate, soil, fire regime, and vegetation are all closely interconnected. The flow chart (figure 3) illustrates the interrelated nature of these physical and biotic factors that determine the timing of colonization and the duration of occupancy by the warbler. Because of the decrease in the occurrence of wildfires due to fire suppression, plantations have become the preferred method of providing warbler habitat. As described here, the landscape ecosystem approach provides resource managers with a useful ecological tool for efficiently locating suitable jack pine plantation sites.
Kirtland's Warbler Citations
For more information
If you would like more information about this project, you can contact either of the researchers through email: Wayne S. Walker or Burton V. Barnes.
Kirtland's Warbler Websites of Interest
Featured Research Project Archives Past Featured Research Projects are stored in the Archives.
|
 |
 |
||
A case in point is the Kirtland's warbler (Dendroica kirtlandii Baird), the rarest member of the wood warbler family in North America. The birds overwinter in the Bahamas and then fly to their summer breeding grounds in northern Lower Michigan. These areas are characterized by flat to gently rolling, dry, glacial outwash plains. The plains support fire-prone stands of jack pine and, to a lesser extent, northern pin oak which are the preferred nesting habitats of the warbler. However, warblers only occupy these pine-oak stands when they are young, i.e., when the pines are 1.5- to 5-meters tall.
On May 5, 1980, what began as a prescribed burn became one of the most intensive wildfires ever recorded in Michigan. In just one day, approximately 24,000 acres were burned across the sandy, outwash-plain basin surrounding Mack Lake in southern Oscoda County. This burn provided the opportunity for studying patterns of warbler occupancy on a landscape ecosystem basis. 
Home | Site Map | Search | © 2007 Ecosystem Management Initiative. Terms of Use