Effects of Drainage‐Basin Geomorphology on Insectivorous Bird Abundance in Temperate Forests |
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Authors: | TOMOYA IWATA JOTARO URABE HIROMUNE MITSUHASHI |
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Institution: | 1. Faculty of Engineering, University of Yamanashi, Kofu 400‐8511, Japan, email tiwata@yamanashi.ac.jp;2. Graduate School of Life Science, Tohoku University, Sendai 980‐8578, Japan;3. Museum of Nature and Human Activities, Hyogo, Sanda 669‐1546, Japan |
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Abstract: | Abstract: Interfaces between terrestrial and stream ecosystems often enhance species diversity and population abundance of ecological communities beyond levels that would be expected separately from both the ecosystems. Nevertheless, no study has examined how stream configuration within a watershed influences the population of terrestrial predators at the drainage‐basin scale. We examined the habitat and abundance relationships of forest insectivorous birds in eight drainage basins in a cool temperate forest of Japan during spring and summer. Each basin has different drainage‐basin geomorphology, such as the density and frequency of stream channels. In spring, when terrestrial arthropod prey biomass is limited, insectivorous birds aggregated in habitats closer to streams, where emerging aquatic prey was abundant. Nevertheless, birds ceased to aggregate around streams in summer because terrestrial prey became plentiful. Watershed‐scale analyses showed that drainage basins with longer stream channels per unit area sustained higher densities of insectivorous birds. Moreover, such effects of streams on birds continued from spring through summer, even though birds dispersed out of riparian areas in the summer. Although our data are from only a single year, our findings imply that physical modifications of stream channels may reduce populations of forest birds; thus, they emphasize the importance of landscape‐based management approaches that consider both stream and forest ecosystems for watershed biodiversity conservation. |
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Keywords: | bird distribution cool temperate forest drainage basin geomorphology riparian landscape stream subsidy watershed scale bosque templado cuenca distribució n de aves escala de cuenca geomorfologí a paisaje ribereñ o subsidio de arroyo |
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