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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123. No. 2. June 2011 
FIG. 3. Ground cover measurements in I-m 2 plots in a stand used by Kirtland's Warblers in Adams County. Wisconsin 
in 2009. Error bars are 95% confidence intervals. Means are from 40 plots, except for grasses and sedges, which are from 
26 plots we separately recorded for those two cover types. The mean of grasses + sedges was recorded for all 40 plots, and 
was 46.1% (95% Cl = 35.7, 56.4). 
have reported the tendency of Care .r pensylvanica 
to form dense mats in jack pine stands following 
disturbance, which may inhibit growth of blue¬ 
berry and jack pine (Abrams and Dickmann 1982, 
Houseman and Anderson 2002, Probst and 
Donnerwright 2003). Probst and Donnerwright 
(2003) noted that ground cover does not seem to 
be a limiting factor for Kirtland’s Warbler nest 
sites or habitat suitability, as a wide range of 
ground cover types occurs on appropriate sites. 
CONSERVATION IMPLICATIONS 
The extensive die-off of planted red pine and 
substantial natural jack pine recruitment at the 
Adams County site provided a landscape matrix 
of openings and thickets that produced suitable 
Kirtland’s Warbler habitat. We believe that, 
except for these circumstances, this stand would 
not be suitable for occupation by Kirtland's 
Warblers, and that most planted red pine planta¬ 
tions do not create the habitat conditions required 
by the species. Future management mimicking the 
conditions at our site, featuring thickets of jack 
Pine complementing reduced numbers of red pine 
interspersed with openings (see Probst 1988) 
could prove fruitful. The inclusion of more- 
profitable red pine in this configuration might 
provide an incentive for timber companies to plant 
some stands in configurations that support Kirt¬ 
land’s Warblers, resulting in supplemental habitat 
beyond traditional jack pine stands. 
Understanding the characteristics of future 
occupied stands throughout the area of range 
expansion is essential if the total Kirtland's 
Warbler population continues to increase. The 
potential suitability of red pine-dominated sites 
could become increasingly important if jack pine 
continues to be converted to red pine. More study 
is needed on the characteristics that affect 
suitability ol red pine-dominated stands for Kirt- 
land s Warblers, especially how suitability of 
these sites changes over time. 
ACKNOWLEDGMENTS 
Hie Natural Resources Foundation of Wisconsin and 
Wisconsin Society for Ornithology provided funding for this 
research. Wc thank Plum Creek Timber for assistance and T. 
A. Watson lor providing maps and information about the 
stands. We are indebted to D. J. DiTommaso for finding and 
monitoring birds in 2007. We thank J. R. Probst for 
assistance in the field and many productive discussions that 
contributed ideas to this manuscript. J. R. Probst. R. L. 
