山階鳥類学雑誌
Online ISSN : 1882-0999
Print ISSN : 1348-5032
ISSN-L : 1348-5032
39 巻 , 2 号
選択された号の論文の7件中1~7を表示しています
原著論文
  • 中村 和雄
    2008 年 39 巻 2 号 p. 69-86
    発行日: 2008/03/20
    公開日: 2010/03/20
    ジャーナル フリー
    In the plains of Kanto district, Japan, flocks of the Brown-eared Bulbul Hypsipetes amaurotis often undertake a southern autumn migration. From 1934 to 1942 Mr. Genzaburo Saito made daily observations throughout the annual autumn migrations at Chiba City, Chiba Prefecture, and recorded values of several migration parameters. I analyzed his data to clarify the migration status c. 70 years ago and to assess whether the status differed from the present one. Results showed the annual number of migrating individuals to vary from c. 400 to c. 1,700 with a median of c. 900 and c. 14 individuals in a flock. Flights began in late September and finished in early November, with most flocks flying in October. Comparison with the data of Yamaguchi (2004, 2005) revealed the values obtained at Chiba City c. 70 years ago do not differ greatly from those occurring at the present time. Therefore, even though part of the H. amaurotis population has begun to breed in the plain regions in west-southern districts in Japan over the past 70 years, the migration status has remained unchanged. During each migration period, the number of migrating birds showed at least two peaks. The mean time at which peaks occurred differed between days, suggesting that the site at which each flock had started to fly was respectively different. Flocks arrived from the northwest and departed in a southeasterly direction, and the variance of the direction was very small. As this direction is parallel to the coastline at Chiba City, the birds may fly along the coastline towards the southern part of Boso peninsula where Chiba City is located. However, some flocks may visit forests en route, and remain there for a time. Therefore, autumn migrating flocks of H. amaurotis are thought to show a flexible behaviour responding to environmental conditions.
  • 原田 知子, 出口 智広, Brenda Zaun, Rachel Seabury Sprague, Judy Jacobs
    2008 年 39 巻 2 号 p. 87-100
    発行日: 2008/03/20
    公開日: 2010/03/20
    ジャーナル フリー
    The population of endangered Short-tailed Albatrosses Phoebastria albatrus has gradually increased through great conservational efforts, but their only two breeding sites, Torishima Island and Senkaku Islands, have a high risk of volcanic eruption or political problems. The Short-tailed Albatross Recovery Team has indicated that, to achieve recovery of this species, additional breeding colonies of the Short-tailed Albatross must be established. Their proposed plan is to artificially rear chicks translocated from Torishima Island at new safe sites. To evaluate the feasibility of this approach, it is important that trials first be conducted with related albatross species. In early March of 2006, 10 Laysan Albatross P. immutabilis, approximately one month of age, were captured at Midway Atoll and moved to Kauai Island, where we attempted to rear them to fledging in early July. Chicks were provided daily with 250-450 g of squid and lake smelt as food. This amount was estimated from a regression equation derived from the proportion of daily amount of food to body mass and daily increase of body mass in the Grey-headed Albatross Diomedea chrysostoma. This species has a similar growth pattern as the Laysan Albatross. We also provided vitamins and other supplements to compensate for nutritional deficiencies in the diet, along with some electrolyte solution to prevent dehydration. Three and two chicks died during one month after beginning to rear and just before fledging, respectively. One chick with an injured wing and no prospect of flying was housed at Monterey Bay Aquarium. The remaining four chicks fledged successfully. Sources of mortality included exposure and bacterial infections in their gastro-intestine. Although we had to feed them greater amounts of food than that estimated from the regression, the captive chicks achieved the same trajectory of mass growth as wild chicks. Improved hygiene of food and equipment, and better techniques for handling of chicks will be adopted in future rearing efforts.
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