Abstract
The ecological adaptations made by the Ogasawara Greenfinch Carduelis sinica kittlitzi on the Ogasawara Islands, and its present situation, were studied during the periods 24-31 December 1995 and 4-10 April 1996. Their main breeding area was the small islands around Hahajima, and their distribution was closely related to the distribution of arid shrubs. They were mainly observed in an environment of arid shrubs. Feeding behaviours in breeding season were most frequently observed on the ground, amongst arid shrubs. Nests were found in trees, in arid shrubs, and in adjacent groves. Mean clutch size was 3.5, a size smaller than that of other popultations of the Japanese Greenfinch C. sinica minor. Mean egg size, however, was larger than that of other populations. Food items in breeding season were mainly the seeds of arid shrubs, as opposed to the seeds of grasses with other populations of Japanese Greenfinches. In spite of its small body size, the Ogasawara Greenfinches has a large bill and a longer tarsus length, given the geographic latitude at which they live. From these facts, it was concluded that Ogasawara Greenfinches have adapted to the arid shrub on the Ogasawara Islands: their large bill and long tarsus length constitute adaptations to the need to forage for seeds among the arid shrubs; their small body size and small clutch size are adaptations to subtropical climate; and their movement after breeding season to the main island of Hahajima is a moult migration closely related to the shortage of food and water during the summer season.
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