Wood and Perkins • CERULEAN WARBLER ACTIVITIES 
501 
TABLE 3. Use of vegetative strata for singing and foraging in core and non-core areas of territories and for singing 
in association with canopy gaps by male Cerulean Warblers, Wetzel County, West Virginia, May—June 2005. The 
standardized residual (SR) values farthest from zero indicate the greatest differences between observed and expected values 
(numbers of observations) of individual cells. 
Vegetative strata 
Singing 
Foraging 
Singing 
Core 
Non-core 
Core 
Non-core 
Gap 
No Gap 
Midstory 
Observed 
24 
31 
1 
8 
15 
40 
Expected 
30.3 
24.7 
3.1 
5.9 
18.8 
36.2 
SR 
-1.14 
1.26 
-1.18 
0.85 
-0.88 
0.63 
Lower-canopy 
Observed 
83 
78 
9 
30 
37 
124 
Expected 
88.6 
72.4 
13.3 
25.7 
55.0 
106.0 
SR 
-0.60 
0.66 
-1.18 
0.85 
-2.43 
1.75 
Mid-canopy 
Observed 
72 
60 
19 
12 
49 
83 
Expected 
72.7 
59.3 
10.6 
20.4 
45.1 
86.9 
SR. 
-0.08 
0.09 
2.59 
-1.87 
0.58 
-0.42 
Upper-canopy 
Observed 
61 
27 
1 
8 
48 
40 
Expected 
48.4 
39.6 
3.1 
5.9 
30.1 
57.9 
SR 
1.80 
-2.00 
-1.18 
0.85 
3.27 
-2.36 
expected within core areas and less than expected 
outside of core areas (Table 3). Mid-story singing 
locations occurred more than expected outside 
of core areas and less than expected within core 
areas. Lower- and mid-canopy singing locations 
were observed equally in core and non-core 
areas. Singing locations in the upper-canopy were 
associated with canopy gaps more than expected 
(Table 3). 
Use of vegetative strata for foraging differed 
between core and non-core areas (x 2 = 16.54. 
df = 3, P = 0.0009). We detected the greatest 
difference between observed and expected values 
in the mid-canopy strata (Table 3) where foraging 
occurred in this stratum more frequently than 
expected within core areas and less than expected 
in non-core areas. 
Males were associated with canopy gaps during 
34% (/, = 234 of 685) of observations on Hail 
Ridge and 19% (// = 54 of 278) of observations 
on Snake Ridge. Activity associated with canopy 
gaps did not differ front that away from gaps (x 2 
= 6.98. df = 3. P = 0.07; Fisher’s exact test P = 
0-06; Table 2). 
We observed Cerulean Warbler males using 23 
different tree species on the two sites (Table 4) 
for a variety of activities. Oaks were used most 
commonly on the xeric site (Snake Ridge) 
whereas black cherry and black locust were used 
most often on Hart Ridge. Singing and foraging 
activity did not differ among tree species on Hart 
Ridge (x 2 = 12.42. df = 8. P = 0.13). We 
recorded too few foraging observations on Snake 
Ridge to make this comparison. The distribution 
of tree species used for singing differed between 
core and non-core areas on Hart Ridge (x~ = 
28.29. df = 6. P < 0.0001) and on Snake Ridge 
(X 2 = 18.16. df - 2, P < 0.0001). Males used 
black cherry on Hart Ridge and species of hickory 
(Table 4) on Snake Ridge more in core areas than 
non-core areas (Fig. 1). 
DISCUSSION 
The Cerulean Warbler is a canopy associated 
species. They forage by gleaning insects off 
leaves and twigs in the forest canopy, place nests 
in the forest canopy at heights up to 30 m, and 
sing in the canopy (Hamel 2000a. b). However, 
data regarding canopy levels exploited for sing¬ 
ing, foraging, and other behaviors are limited. 
Barg et al. (2006) reported higher mean singing 
heights (15 m) than foraging heights (12.8 m) in 
Ontario. We found that activity type varied among 
vegetative strata, which may help explain Ceru¬ 
lean Warbler preference for a vertically stratified 
canopy. Singing occurred more than expected in 
