PELLET ANALYSIS OF THE BULL-HEADED SHRIKE <i>LANIUS BUCEPHALUS</i> AND THE SEASONAL CHANGE OF FOOD HABITS

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  • OGAWA Iwao
    Institute of Applied Zoology, Faculty of Agriculture, Hokkaido University

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  • ペリットによるモズの食性分析とその季節変化
  • ペリット ニヨル モズ ノ ショクセイ ブンセキ ト ソノ キセツ ヘンカ

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Abstract

This study was carried out to clarify the food habits of the Bull-headed Shrike Lanius bucephalus by analyzing the contents of pellets. These pellets were collected in Iwata, Shizuoka prefecture from March to April in 1972 and from October in 1972 to April in 1973 excepting November. During the 8 months 151 pellets were collected, from which 1470 preys were sorted out. The results are as follows.<br>1. The average length of pellets was 18.3mm (10-30mm) and the average thickness was 9.1mm (7-11mm).<br>2. Insects constituted the largest percentage of the invertebrates, consisting of 57 genus, and many other invertebrates such as spiders, sow bugs and centipedes appeared. Some vertebrates such as birds, voles and frogs appeared. In addition to animal preys, small number of plant seeds, e.g. those of Euonymus japonicus and Ligustrum japonicum were found.<br>3. The most abundant was Coleoptera (57.5%), in which Harpalidae was most favored and was higher in percentage in the breeding season than in the nonbreeding season. Insects such as Pyrrhocoridae and Vespidae were next abundant. Appearance of plant seeds in the pellets was scanty or nill except in October.<br>4. Seasonal change of preys involved in pellets differed in the pattern accoding to the species or group of it. Some species of Vespidae, Chrysomelidae, Gryllotalpidae Gryllotalpa africana and Acrididae Locusta migratoria decreased gradually from autumn to spring, while Harpalidae and sow bugs increased on the contrary during the same season.<br>5. The food habits of the Bull-headed Shrike which were elucidated by the pellet analysis were different from the results of stomach analyses and the larder records of the same species studied in the past, and also from the food habits of the Great Grey Shrike L. excubitor, especially in the high portion of Harpalidae in the foods. These differences were discussed with relation to the characteristic feeding ecology of the Bull-headed Shrike.

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