Anich et al • KIRTLAND’S WARBLERS IN RED PINE 
201 
territories of six males. We obtained data that best 
represented the general nesting habitat at the site 
by placing transects in the occupied cluster. 
Transects were east-west to avoid sampling 
artifacts from north-south planted rows of red 
pine. Transects averaged 375 m in length and 
were 100 m apart with 11-15 points per transect. 
We used point-quarter sampling (Cottam and 
Curtis 1956) and measured the distance to and 
species of the nearest tree in each quadrant 
surrounding each point, allowing us to calculate 
tree density and relative frequency. We also 
measured tree height and height of the lowest 
green branch. We only measured trees that were 
^2.5 cm in diameter at 10 cm from the ground. 
We also quantified ground cover below 50 cm in a 
I-nr quadrat centered at the point. Cover types 
were classified as blueberry, grasses/sedges, live 
woody stems, moss/lichens, bare ground, dead 
woody debris, forbs, pine needles, or leaf litter. 
We recorded grass and sedge cover separately for 
26 of the 40 plots. We used tape measures across 
548 m of our transects and quantified the distance 
(to the nearest 0.03 m) comprised by open area or 
canopy cover of the three major tree species. 
Data Analysis .—We used descriptive statistics 
to summarize the data. We report number of birds 
detected and calculate return rate of color-banded 
males. We report the number of nests, number 
successful, and estimated number of young 
fledged. We summarized the data for the stand 
vegetation measurements using means and 95% 
confidence intervals (Cl). We used the 95% Cl to 
compare stand tree heights and lowest live branch 
heights to previously published results from 
Michigan Kirtland’s Warbler breeding areas, 
specifically wildfire-regeneration areas and plan¬ 
tations (Probst and Wcinrich 1993. Bocetti 1994). 
RESULTS 
Occupancy and Nest Success .—Red pine stands 
occupied by Kirtland’.s Warblers in Adams 
County in 2008 and 2009 ranged in age from 11 
to 13 years (since 2-year-old seedlings were 
planted) and ranged in size from 36 to 70 ha (T. 
A. Watson, pers. comm.). Eight male and five 
female Kirtland’s Warblers were detected in 2008. 
Five of seven males (71%) color-banded in 2008 
returned to the site in 2009. Ten male and 10 
female Kirtland’s Warblers were found in 2009. 
We located five nests in 2008, two of which 
fledged five Kirtland’.s Warbler young each. We 
found 10 nests in 2009. of which at least six 
successfully fledged an estimated 23 warbler 
young. Three of four stands used by Kirtland’s 
Warbler between 2007 and 2009 were within 
3 km. We also detected a single pair in 2009 that 
successfully nested in a fourth stand, 10 km from 
the main stands. 
Habitat Characteristics .—Total density of trees 
was 1,876/ha of which 66.9% were red pine 
(1,254/ha), 20.6% were oak (387/ha), and 12.5% 
were jack pine (234/ha). Mean tree height was 
3.2 m (Fig. 1). Jack pines in the Wisconsin stand 
were taller than in the Michigan stands, while 
heights of red pines were similar (Fig. 1). Most 
oaks at our site were small (mean height — 2.2 m, 
95% Cl = [1.9. 2.4J. n = 33). The height of the 
lowest live branches of jack pine on the 
Wisconsin site was similar to heights reported in 
Michigan (Fig. 2). The lowest live branch of red 
pine in the Wisconsin stand was closer to the 
forest floor than for jack pine (Fig. 2). The canopy 
in the Wisconsin stand was over half open (54%) 
with red pine dominating the tree canopy (31% 
cover) followed by oak (9%) and jack pine (6%). 
Ground cover in the stand was dominated by 
sedges followed by pine needles and dead woody 
debris (Fig. 3). We recorded relatively few blue¬ 
berries, forbs, and grasses. Big blucstem (Andro- 
pogon gerardii) was the most common grass in our 
plots. The most common forb recorded was 
flowering spurge (Euphorbia carol lata), which 
was present in 15 of 40 plots (38%). Long-branch 
frostweed (Helianthemum canadense), common 
sheep sorrel (Rumex acetusellu); and starry false 
Solomon’s seal (Maianthemum stellatum) were 
each present in four plots. 
DISCUSSION 
Red pine is not a common breeding habitat for 
Kirtland's Warblers, but the persistent occupancy, 
comparable return rates to that found for birds in 
jack pine stands, and good nest success demon¬ 
strated the suitability of red pine-dominated 
stands for breeding Kirtland's Warblers. All four 
stands in Adams County selected for use by 
Kirtland's Warblers were red pine plantations. 
The return rate for our small sample of adult 
males is comparable to reported rates from 
Michigan of 53-75% (Berger and Radabaugh 
1968: Mayfield 1960, 1983; Probst 1986) sug¬ 
gesting males survive and perceive the Adams 
County site as suitable habitat. Hoover (2003) 
suggested site fidelity is associated with site 
quality because birds that breed successfully are 
