Journal of the Yamashina Institute for Ornithology
Online ISSN : 1882-0999
Print ISSN : 1348-5032
Volume 39 , Issue 2
Showing 1-7 articles out of 7 articles from the selected issue
Original Articles
  • Kazuo Nakamura
    2008 Volume 39 Issue 2 Pages 69-86
    Published: March 20, 2008
    Released: March 20, 2010
    JOURNALS FREE ACCESS
    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.
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  • Tomoko Harada, Tomohiro Deguchi, Brenda Zaun, Rachel Seabury Sprague, ...
    2008 Volume 39 Issue 2 Pages 87-100
    Published: March 20, 2008
    Released: March 20, 2010
    JOURNALS FREE ACCESS
    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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Short Notes
  • Akira Mizutani, Hiroyoshi Kohno
    2008 Volume 39 Issue 2 Pages 101-111
    Published: March 20, 2008
    Released: March 20, 2010
    JOURNALS FREE ACCESS
    The distribution of breeding sites, number of nests, and timing of egg laying of the threatened Black-naped Tern Sterna sumatrana and Roseate Tern S. dougallii was surveyed across most of the Yaeyama Islands, located among the southern Ryukyu Islands, in the 2001 breeding season. Black-naped Terns bred in 42 sites that included 1-64 nests (average number of nests, 14.8±16.5 SD). Roseate Terns bred in six sites that included 1-123 nests (average number of nests, 59.8±57.3 SD). At most of the breeding sites, Black-naped Terns started to lay eggs in late June; while at some breeding sites, breeding commenced in early or mid July. Roseate Terns started to lay eggs in late June at two sites and in mid June at the other site.
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  • Kentaro Kazama, Kentaro Q. Sakamoto, Yutaka Watanuki
    2008 Volume 39 Issue 2 Pages 112-116
    Published: March 20, 2008
    Released: March 20, 2010
    JOURNALS FREE ACCESS
    In some avian species, male plasma testosterone levels are maximum during the courtship or copulation periods, but decline abruptly once incubation starts. However, testosterone levels of male Black-tailed Gulls Larus crassirostris during the course of breeding remain unknown. In 2006, blood samples of 23 incubating males were collected at Rishiri Island, Hokkaido, Japan and testosterone was measured by enzyme immunoassay kit. Plasma testosterone level (mean±S.E.: 0.737±0.282 ng/ml) was assumed to decline with elapsed days from the onset of incubation, as shown in other species.
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