O'Brien and Riichison • NON-BREEDING ECOLOGY OF SHRIKES 
363 
TABLE 3. Mean ± SE characteristics of vegetation 
associated with isolated perches used (n = 21) by 
Loggerhead Shrikes (n = 7) and randomly selected, 
apparently unused, isolated perches (n = 21) in 
Kentucky. Differences are significant (P = 0.023). 
Viriable 
Used 
Random 
Litter depth (cm) 
1.24 ± 0.18 
0.58 ±0.18 
Vegetation height (cm) 
12.7 ± 1.3 
11.4 ± 2.3 
Foliage cover <0.5 m 
(# of stems) 
12.6 ± 0.9 
10.6 ± 0.8 
Ground cover (%) 
Grass 
72.2 ± 2.9 
71.2 ± 5.0 
Herb 
2.7 ± 1.5 
9.1 ± 3.3 
Litter 
4.7 ± 1.4 
6.7 ± 3.3 
Bare ground 
17.8 ± 2.5 
10.5 ± 3.1 
The characteristics of isolated perches used by 
shrikes and randomly selected, apparently unused 
isolated perches differed (Wilks* X. = 0.50. F 9 32 = 
3-3. P = 0.0023). Stepwise discriminant analysis 
revealed that litter depth, percent bare ground, and 
foliage cover below 0.5 m permitted the best 
discrimination between used and random isolated 
perches. Classification analysis correctly catego- 
ttzed 81.0% of randomly selected perches and 
77.4% of used perches. Used perches had deeper 
litter, more bare ground, and more foliage cover 
<0.5 m than randomly selected perches (Table 3). 
Territory Characteristics .—The mean ± SE 
mzc of Loggerhead Shrike territories (n = 7) 
during the non-breeding period was 85.0 ± 
16.7 ha. Shrike territories contained large num- 
kfs of isolated trees (Table 4). Fences were 
present in all territories and utility wires (Table 4) 
w ere present in six of seven territories ( 86 %). 
Hayfield was the most common habitat type 
(Table 4). We found no difference between the 
L 'haracteristics of shrike territories and randomly 
selected, apparently unoccupied areas (Wilks' 
= 0-02, F 12i , = 4.5, P = 0.36; Table 4). 
Mortality .—Two radio-marked shrikes were 
tilled by predators 9 and 15 days, respectively. 
a,Ier being radio-marked. Based on the presence 
plucked feathers near transmitters, these shrikes 
were probably killed by either Cooper’s (Accipiter 
cooperii) or Sharp-shinned (A. xtriatus ) hawks. 
DISCUSSION 
Hunting Behavior: Prey U.se.— Insects and 
lf >vertebrates were the most common prey of 
Loggerhead Shrikes in our study, and only eight 
vertebrates were taken as prey. Similar results 
TABLE 4. Mean ± SE habitat characteristics of used 
Loggerhead Shrike territories compared with unused areas 
in Kentucky. Differences are not significant. 
Used 
Unused 
Non-thorny (number) 
Trees 
222.9 ±31.3 
248.0 ± 36.7 
Shrubs 
9.0 ± 3.8 
24.0 ± 14.0 
Thorny (number) 
Trees 
63.9 ± 8.4 
59.0 ± 14.2 
Shrubs 
24.9 ±18.1 
24.0 ± 5.1 
Habitat types (%) 
Hayfield 
69.3 ± 8.2 
67.8 ± 8.2 
Pasture 
11.4 ± 8.8 
11.5 ± 4.3 
Woodlot 
14.9 ± 3.9 
12.7 ± 4.2 
Crop 
4.4 ± 2.5 
2.2 ± 1.1 
Old field 
0 
5.8 ± 3.6 
Linear structures/habitat (km) 
Fencelinc 
3.9 ± 1.0 
5.5 ± 0.3 
Utility wires 
0.9 ± 0.4 
2.0 ± 0.6 
Woodrow 
3.7 ± 0.6 
3.2 ± 0.8 
were reported for shrikes during the breeding 
season in the same area of central Kentucky with 
arthropods the most common prey (Olson 2006, 
Peterson 2006). Other investigators have also 
reported insects are typically the most common 
prey of Loggerhead Shrikes during both the 
breeding and non-breeding seasons ( Yosef 1996). 
Hunting Behavior: Attacks and Outcomes — 
The outcome of hunting attempts by shrikes in our 
study (attacked or gave up and. for attacks, 
whether successful or unsuccessful) had no effect 
on mean perch time, perch height, and attack 
distance. Peterson (2006) examined the hunting 
behavior of Loggerhead Shrikes in the same study 
area (Madison and Garrard counties. Kentucky) 
during the breeding season and reported similar 
results. Similar results have been reported for 
other sit-and-wait predators, including Boreal 
Owls (Aegolius funereus ; Bye et al. 1992) and 
Eastern Screech-Owls (Megascops asio\ Abbruzz- 
ese and Ritchison 1997). 
Perch times of Loggerhead Shrikes were 
similar during the breeding (Olson 2006, Peterson 
2006) and non-breeding (our study) seasons in 
central Kentucky (Table 5). Other investigators 
have found perch times are more affected by prey 
selection than season (Teineles 1985. Bildstein 
1987. Sonerud 1992). The diet of Loggerhead 
Shrikes in central Kentucky consisted primarily of 
invertebrates during both breeding and non- 
