なぜブッポウソウ <i>Eurystomus orientalis</i> は巣に奇妙なものを運ぶのか

書誌事項

タイトル別名
  • Why does the Broad-billed Roller <i>Eurystomus orientalis</i> bring Strange Objects to the Nest?
  • Why does the Broad-billed Roller Eurystomus orientalis bring Strange Objects to the Nest?

抄録

1) Some strange objects, shells, glass, plastic, porcelain, etc., were found from the nests of Broad-billed Rollers Eurystomus orientalis. These objects had some common characteristics; most of them had a hard and shiny surface, and had no nutritional value.<br>2) Using experiments with test objects, we examined when and where these objects were brought to the nest. The experiments showed that most objects were brought to the nests from less than 200 m away.<br>3) Strange objects were brought to the nests mainly at the end of the nestling and copulation period (the most frequent time of feeding). The test objects brought during the copulation period were found both in the area near nest and under nests, while the test objects collected during the nestling perod were from the bottom of nests.<br>4) Most objects (80.6%) collected from the bottom of nests and 41.8% of the objects collected from under the nests were very dirty with small fragments of chitinous parts of insects. The average size of clean objects was larger than that of the dirty objects.<br>5) Some of the test objects removed by Broad-billed Rollers were found to have been folded. All of the deformed test objects were very dirty.<br>6) Most of the dirty aluminium pieces had some scratches on the surface. The aluminium pieces used by Broad-billed Rollers had some scratches on the outer surface, however, there were no scratches on the inner surfaces.<br>7) It was shown that the dirty objects were swallowed by nestlings or parent birds and then regurgitated as pellets, and the scratches left on the surface of the aluminium objects were made by the objects being rubbed together in the bird's stomach. From these observations, it was concluded that the strange objects were used as "millstones" for grinding hard chitinous bodies of beetles, which are main food of Broad-billed Rollers, and to aid digestion.<br>8) The possibility that the objects brought at the nests during the copulation period were used as a tool of courtship display was also discussed.

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詳細情報

  • CRID
    1390001204481702144
  • NII論文ID
    130003564520
    30037479409
  • DOI
    10.3838/jjo.36.137
  • ISSN
    18819710
    0913400X
  • 本文言語コード
    en
  • データソース種別
    • JaLC
    • Crossref
    • CiNii Articles
  • 抄録ライセンスフラグ
    使用不可

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