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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123. No. 2. June 2011 
TABLE 5. Comparison (± SE) of the hunting behavior 
of Loggerhead Shrikes during the non-breeding (this study) 
and breeding (Olson 2006, Peterson 2006) seasons 
in Kentucky. 
Variable This study Olson (2006) Peterson (2006) 
Perch time (min) 2.2 ± 0.1 2.6 ± 0.2 2.9 ± 3.6 
Perch height (m) 2.8 ± 0.1 5.3 ± 0.2 5.1 ± 4.7 
Attack distance (m) 4.3 ± 0.2 10.4 ± 14.1 
breeding seasons and. as a result, perch times 
exhibited no seasonal difference. 
Mean perch height and attack distances in our 
study were less than half those reported for 
Loggerhead Shrikes in the same study area during 
the breeding season (Olson 2006, Peterson 2006; 
Table 5). Morrison (1980) compared the hunting 
behavior of Loggerhead Shrikes during pre- 
breeding (Dec-Mar) and breeding (Mar-Jul) 
periods and found perch heights and attack 
distances increased significantly during the breed¬ 
ing season. Seasonal differences in perch height 
and attack distance may be due to seasonal 
differences in vegetation height. Vegetation at 
perch sites used by shrikes during the non¬ 
breeding season in our study was shorter than at 
perches used during the breeding season in the 
same study area ( Peterson 2006). Shrikes may use 
higher perches when ground vegetation is taller 
and denser to provide “a wider view of 
surrounding vegetation’ * (Morrison 1980: 297). 
Increasing perch height in tall vegetation im¬ 
proves prey visibility, especially for detecting 
prey beneath taller vegetation (Andcrsson et al. 
2009), and also enables predators to detect prey at 
greater distances (Soncrud 1992. Andersson et al. 
2009). The ability to detect prey further from 
higher perches may explain the longer attack 
distances of shrikes during the breeding period. 
Positive relationships between perch height and 
attack distance have also been reported for other 
sit-and-wait predators (Sonerud 1980. 1992 
Carlson 1985). 
Characteristics of Perch Site Habitat .—We 
found perches used by shrikes were generally in 
areas with shorter, but denser vegetation, and 
deeper litter compared to randomly selected, 
apparently unused sites. Other investigators have 
reported Loggerhead Shrikes often occur in areas 
with short vegetation (Bohall-Wood 1987, Smith 
and Kruse 1992, Gawlik and Bildstein 1993). 
However, areas used by shrikes must also exhibit 
some structural heterogeneity or patchiness. For 
example. Michaels and Cully (1998) reported 
shrikes occurred in areas where vegetation 
exhibited high structural heterogeneity, i,e., sites 
with less vegetative cover and more bare ground, 
but with taller vegetation. Structurally complex 
habitats with areas of both shorter vegetation and 
taller (or, as in our study, denser) vegetation may 
provide habitat for a diverse prey base, including 
invertebrates and small mammals, while simulta¬ 
neously enhancing visibility and the ability of 
shrikes to detect prey. 
Territory Characteristics. —Mean territory size 
(85 ha) of Loggerhead Shrikes during the non¬ 
breeding season in our study was larger than 
reported during the breeding season in Kentucky 
(9 ha; Peterson 2006), Missouri (4.6 ha; KrideJ- 
baugh 1982), Alberta (8.5 ha; Collister and 
Wilson 2007), and Florida (8.35-10.1 ha; Yosef 
and Grubb 1993, 1994). Seasonal differences in 
range sizes of Loggerhead Shrikes and. specifi¬ 
cally, the relatively large winter ranges in our 
study, may be due to differences in prey avail¬ 
ability. Yosef and Deyrup (1998) demonstrated 
the effect of prey availability on size of Logger- 
head Shrike territories by experimentally reducing 
insect populations in breeding territories; temtory 
size increased by an average of 138% in response 
to this treatment. 
Characteristics of areas used by Loggerhead 
Shrikes in our study did not differ from those of 
apparently unused areas, indicating apparently 
suitable habitat remained unoccupied. Investiga¬ 
tors have also reported no differences between 
characteristics of breeding territories of Logger- 
head Shrikes and randomly selected, apparently 
unused areas (Brooks and Temple 1990, Esely and 
Bollinger 2001, Fomes 2004, Olson 2006 . Peter¬ 
son 2006). These results suggest that, al least in 
some areas. Loggerhead Shrike populations are 
not limited by availability of suitable habitat- 
Availability of wintering habitat does not 
appear to be a limiting factor for Loggerhead 
Shrikes in central Kentucky, but little is known 
about the quality and availability of wintering 
habitat in other parts of their winter range. Further 
south in their wintering range where densities are 
higher than in Kentucky (Hobson and Wassenaar 
2001, Stedman and Allen 2003, Perez and Hobson 
2007), Loggerhead Shrikes may exhibit intraspe¬ 
cific competition for suitable wintering sites that 
could influence over-winter survival. For exam¬ 
ple, Perez and Hobson (2009) identified resident 
