Effect of forest shape on habitat selection of birds in a plantation-dominant landscape across seasons: comparison between continuous and strip forests
Conversion of natural forests to other land use results not only in a decrease of forest area but also in the degradation of remnant forests as a habitat for forest animals. Although such degradation due to an increase of forest edges has been studied most intensively, other factors such as forest shape may also contribute to the degradation. In this study, we compared bird abundance and species richness between irregular-shaped and relatively continuous forests in the breeding and migratory seasons. Since the forests were surrounded by tree plantations rather than open lands, the edge effect may have been weak at the study site. Our results suggested that the irregular forest shape negatively affected forest bird abundance and species richness in the breeding season, but not in the migratory season. The response of birds varied with bird traits: migrants avoided the irregular-shaped forest, but residents did not. Among the residents, small ones preferred or tolerate the irregular-shaped forest whereas large ones avoided it. This study indicates that careful consideration of various factors such as seasonality and bird traits is needed to understand the consequences of land use changes on forest birds.
KeywordsForest bird Forest shape Migration habit Plantation-dominant landscape Seasonality
We thank Ms. A. Sawa and Mr. H. Yamagata for field assistance; Drs. M. Ushio and R. Koda, E. Nakajima, Mr. T.F. Haraguchi, and members of the Center for Ecological Research for their valuable comments and discussion. We also thank the Ibaraki District Forestry Office for use of their facilities. Two anonymous reviewers and an editor provided constructive and helpful comments. Funding for this research was provided in part by the Ministry of Education, Culture, Sports, Science, and Technology Grant-in-Aid for Scientific Research (A-19201048, C-17570019), the Research Institute for Humanity and Nature (RIHN, P2-2), Global COE Program A06 of Kyoto University, and a JSPS Research Fellowship for Young Scientists to Shoji Naoe.
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