Endo • NEST-SITE CHARACTERISTICS OF BULL-HEADED SHRIKES 
517 
beneficial effect of attaching to more branches, not 
all Bull-headed Shrikes build nests using a high 
number of branches. There are two explanations. 
First, nest-sites in shrubs with many potential 
branches are limited for Bull-headed Shrikes 
breeding in this study area. Second, there may be 
a trade-off between using many branches around the 
nests and other factors concerning nest success. For 
example, an incubating female in a nest with greater 
concealment may have more difficult) seeing an 
approaching predator, leading to higher female 
depredation. McLean et al. (1986) found that nest 
exposure increased the strength of parental mobbing 
behavior. Thus, there may be a trade-off between 
nest concealment and parental behavior. 
My study demonstrated that number of branch¬ 
es surrounding a nest function as a screen to 
conceal and camouflage Bull-headed Shrike nests 
from predators. Future studies should consider the 
role of branches surrounding a nest as a defense 
against nest predation. 
ACKNOWLEDGMENTS 
I am grateful to Toshilaka Suzuki for helpful comments 
and discussion on this study and the manuscript, and David 
Wheatcroft, Shin Matui, Keisuke Ualu. and two referees for 
helpful comments on the manuscript. 1 also thank Hiroshi 
Hasegawa and members of the Laboratory of Animal 
Ecology, Toho University for helpful discussions, 
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