Methods for evaluation of abundance in endangered birds Apalopteron familiare and Carduelis sinica kittlitze

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Apalopteron familiare and Carduelis sinica kittlitze are endemic to the Bonin Islands and are endangered species. Their abundance on Hahajima, which is a main island of the Hahajima Islands, has been repeatedly surveyed by many researchers and institutions. However, there were no examinations on not only convenient but also reliable methods for the evaluation of abundance of the species. In the present work, I explored convenient and reliable methods for the evaluation of abundance of the species.1) Apalopteron familiare : "Song burst method" , termed by the author, was a method by which we count the number of males singing early in the morning before sunrise. Most territorial (breeding) males sing vigorously early in the morning only for about 20-30 mins, though they only rerely sing during the daytime. It is concluded that "song burst method" is very convenient and reliable to estimate the number of breeding males.2) Carduelis sinica kittlitze : This is an endangered island subspecies of Carduelis sinica. For a long period, surveys have been conducted mainly on the main part of Hahajima. But the birds were mainly distributed over large Islets of Hahajima and at times on the southern part of Hahajima. It was therefore concluded that it is appropriate to count the number of Carduelis sinica kittlitze on those areas to know abundance of this species.