Prey distribution,foliage structure,and foraging behavior of insectivorous birds in two oak species (<Emphasis Type="Italic">Quercus serrata</Emphasis> and <Emphasis Type="Italic">Q. variabilis</Emphasis>) |
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Authors: | Chan-Ryul Park Teruaki Hino Hiroki Itô |
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Institution: | (1) Kansai Research Center, Forestry and Forest Products Research Institute, Kyoto 612-0855, Japan;(2) Present address: Division of Forest Ecology, Korea Forest Research Institute, Seoul, 130-712, Korea;(3) Present address: Tama Forest Science Garden, Forestry and Forest Products Research Institute, Hachioji 193-0843, Japan |
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Abstract: | We examined foraging behaviors of four insectivorous bird species (Great Tit Parus major, Varied Tit P. varius, Long-tailed Tit Aegithalos caudatus and Japanese White-eye Zosterops japonica) on the two oak species (Q. serrata and Q. variabilis) in relation to fine-scale foliage structures, abundance, and distribution of folivorous insects and physical and chemical
characteristics of leaves. There was no difference in the mean number of insects for each oak species, but there was a significant
difference in the mean biomass. The distance from twigs or branches to leaf tips or blade-petiole junctions showed that leaves
of Q. variabilis were more dispersed than those of Q. serrata. The different size distribution of insects influenced insect sizes selected and foraging maneuvers used by each bird species.
Parus major and P.
varius fed on beetles (low energy gain) with perch-gleaning (the most energy-saving maneuver) from the upper side of leaves on Q. variabilis, whereas they fed on large lepidopteran larvae (high energy gain) from the lower side of leaves on Q. serrata using a variety of maneuvers (including energy-consuming ones). Both A. caudatus and Z. japonica fed on insects from the lower side of leaves by hang-gleaning and reach-gleaning, respectively. These species appeared to
be morphologically adapted to the energy-consuming but more effective maneuvers used to take preys from the undersides of
leaves. We hypothesize that differences in foliage structures between closely related species of trees have evolved as a balance
between defense against folivorous insects and attraction of insectivorous birds. |
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Keywords: | Foraging behavior Tree preference Quercus serrata Q variabilis Prey-size selection |
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