Stable isotope analysis has been recognized as a useful tool in ecological science. The reason is that stable isotope ratio change with given enrichment factor through food chain: stable carbon isotope ratio in an animal become close to that of diet. Stable nitrogen isotope ratio in it reveal stepwise enrichment with generally recognized enrichment factor of 3.4±1.0‰. Conventional methods for diet analysis, such as content analysis of digestive organs, provide "snap-shot information" on diet of birds. And there is possibility to overor underestimate diet composition due to different digestive rate on different diet components. In contrast, stable isotope analysis overcame these problem, since isotope ratio in animals reflects the ratio of assimilated diet. As additional information, turnover rate of carbon stable isotope in bird tissues and enrichment factor of carbon and nitrogen isotopes between diets and various kinds of bird tissues have been confirmed. These knowledge supported to evaluate diet of birds in different period from a week to over a year. Based on these understanding, stable isotope analysis have been applied to bird ecology: to reconstruct diet composition, to evaluate relative contribution of various kinds of diets, to trace movements in wintering sites and migration pattern, to estimate carbon and nitrogen cycles in rookeries, and to assess physiological condition of birds. These researches suggested that stable isotope analysis is powerful tool in avian ecology. In future research more laboratory experiments should be required to assess ecological, physiological and biochemical dynamics of isotopes through metabolic process in body of birds and assimilation process of diet components. In addition, multiple use of stable isotopes not only carbon and nitrogen, but also hydrogen, oxygen, sulfur and strontium will also be expected to get insight of bird life such as migration movement of birds.
Conserving birds in urban environments requires ecological information that can be applied to city planning and designing, but few ecological studies on bird communities in residential area have so far been made. I conducted surveys of the terrestrial bird communities at 12 locations in a residential area of Tokyo, Japan in both the breeding and wintering seasons in 1990-91, and identified habitat features associated with bird communities. In both seasons, the residential areas with abundant vegetation supported more species and higher densities of birds. Number of trees (>8m in height) and average tree height were the most significant variables for explaining variances of diversity of bird species among study plots. Abundance and height of buildings were negative factors for diversity in the wintering season, conversely they were positive in the breeding season. Most bird species preferred to use land covered by vegetation. Land occupied by buildings and bare land tended to be avoided by birds and used by fewer species than expected. It was confirmed that vegetation, especially trees, was the key element for bird conservation in residential areas. I present environmental guidelines required for bird conservation in residential areas.
One male and one female Japanese Cormorants, Phalacrocorax filamentosus, breeding at Teuri Island, Hokkaido, foraged within 5km of the island and in the strait between the island and mainland (17-27km from the island). The foraging range of Japanese Cormorants appeared to be limited to the neritic water between 10 and 60m sea depth, where the seabed sediment was mainly rock and sand. Both birds showed high foraging site fidelity, with the male foraging to the south-east and the female to the north-east of the island. The male sometimes foraged in shallow water (<40m), possibly feeding on demersal fish. In deep water (>40m), the male may have fed on epipelagic schooling fish. In contrast, the female did not reach the sea-bottom in deep or shallow waters, and it may have fed on epipelagic schooling fish.
We analyzed 44 Rhinoceros Auklets impacted by the oil spill along the Tsushima Warm Current off Shimane Prefecture, southern Japan Sea in January 1986. All of the carcasses had been oiled with an average of 128g oil weight (ranging from 12 to 300g), which accounted for an average of 31% (ranging from 4 to 72%) of the body mass, and with an average of 40% oiled area of the body surface with wings extended (ranging from 10 to 95%) (n=38). Among the 44 oiled birds, six birds had a few scales and/or vertebrae of fish in digestive organs, but the remaining 38 birds contained no food items. The non-oily blackish liquid contents were found in digestive organs from 34 birds, while blackish liquid was not found in either the esophagus, stomach or intestine of the remaining 10 birds. Neither the presence of the blackish liquid nor the volume found within the digestive organs were correlated with the weight or the area of the oil adhering to the body. This showed that the mortality of oiled birds was independent of the amount of oil adhering to the body and was also independent of the presence or volume of blackish liquid in digestive organs. The oil adhering to the body was detremined to be heavy oil; however, the blackish liquid from within the oiled birds differed greatly from the external oil as seen by gas chromatographic analysis and was considered not to be composed of the n-alkanes identified in the oil adhering to the body or in the oil spilled in the sea. The n-alkane distribution was, however, very similar in the lighter alkanes around C19 and in the phytane and pristane of biomarkers to the liquid contents found in the dead non-oiled bird of the same species washed up on a Pacific-facing beach in central Japan. Petroleum composition analyses, with large sample sizes, of alimentary liquid found in seabirds are needed to clarify the extent to which oil-pollution affects seabirds around Japan in areas that have experienced accidental oil spills and in those that have not.