Birds play a fundamental global role in shaping and maintaining plant populations and communities, by acting as seed dispersers. This review introduces mutualism between birds and plants, particularly endozoochory by frugivorous birds and synzoochory by some granivorous birds, and overviews the impacts of their seed dispersal on ecological and evolutionary processes of plants. First, general associations between these seed dispersal modes and avian feeding strategies are introduced, highlighting current knowledge of patterns of interaction networks between bird and plant communities. Then, plant intrinsic factors, such as fruit and seed characteristics, that are responsible for shaping plant-bird mutualism are summarized for fleshy fruits, and the ways in which the evolution of fruit and seed traits is driven by their mutualism is overviewed. In the next step, the impacts of seed dispersal by birds on plant populations and communities are explained, with emphasis on its roles in driving ecological processes at three different spatial scales (local, landscape, and regional). Lastly, future perspectives of seed dispersal research are discussed. I highlight the importance of integration of various approaches, including natural history studies on the interactions, field studies focusing on plant demography and animal behavior, and statistical modeling of large-scale empirical data, for further exploration of the ecology and evolution of plant-bird mutualism.

In order to promote the conservation and restoration of biodiversity, it is necessary to: quantitatively assess the current status of biodiversity, identify the factors causing its degradation and decline, and consider and implement necessary measures, for each of which long-term monitoring is essential. In Japan, monitoring of wildlife (including birds), and of ecosystems, has been conducted for many years. Avian monitoring has a long history in Japan compared with other countries in Asia. However, the analysis of such monitoring data has not progressed well, and neither monitoring data nor the results of its analysis have been fully utilized in bird conservation management and policy. In this paper, we summarise the current status of avian monitoring in Japan following a questionnaire survey of wetlands designated as an East Asian-Australasian Flyway Partnership Flyway Network Site, and from information collected via the Internet. National-scale monitoring, such as the Monitoring Site 1000 scheme, the Bird Banding Scheme, and regional-scale monitoring such as the survey of the distribution of geese have been carried out. In addition, site-specific bird monitoring has also been conducted at many wetlands, and some monitoring had been conducted for more than 30 years. The existing studies analyzing monitoring data have revealed: 1) population trends, 2) changes in phenology, 3) changes in distribution, and 4) changes in avian communities. Research cases relevant to each topic are summarised mainly focusing on domestic studies. Necessary future research is discussed in relation to three groups of migratory waterbird species (waterfowl, cranes, and shorebirds).

Several non-native bird species established in Japan are believed to have originated from pet birds that were accidentally or intentionally released. Many initial sightings of these non-native birds in the natural environments in the Japanese archipelago were reported during the Taisho-Showa period (1920s to 1980s). We investigated pet bird-keeping practices in Japan during this period by examining magazines and books on the subject published at the time. Our survey revealed that over 40 titles of pet bird magazines were published during the Taisho and early Showa periods. Pet bird keeping was popular for various reasons, including as hobbies, side jobs, academic interests, and speculative investments. However, proper techniques and knowledge for bird keeping were underdeveloped. Additionally, domestic and international political and economic instability, including wars and economic depression, likely led many owners to release their birds into the wild.

The avifauna of the Bayonnaise Rocks, Smith Island and Lot's wife in the Zunan Islands, which form the southern part of the Izu Islands, have not been surveyed in recent years and represent an information gap in the distribution of Japanese birds. Therefore, we conducted observation surveys of the area from 2019 to 2023. The results showed that the number of Brown Booby Sula leucogaster has increased since the 1960s, with a maximum of about 600 individuals observed on Lot's Wife. This is thought to be due to an increase in the population in the Ogasawara Islands, located to the south, as a result of a nature restoration project there. Additionally, Brewster's Brown Booby S. leucogaster brewsteri, Masked Booby S. dactylatra, Red-footed Booby S. sula and Nazca Booby S. granti were all observed on the islands for the first time. The Red-footed Booby was particularly abundant with a maximum of 80 individuals on Lot's Wife, and its distribution has expanded nationwide since the late 20th century, with recent confirmation of colonies on the Yaeyama and Volcano Islands. This range expansion may be due to population increases at breeding sites outside Japan.

In 2015, the captive breeding of Japanese Night Heron Gorsachius goisagi was successfully achieved for the first time in Japan. Information on the species' breeding biology is generally lacking because of the difficulty in obtaining detailed field observations. In this study, we recorded detailed information on the reproductive behavior of two captive pairs, the individuals of which were identifiable by their leg bands. The start of the breeding season and the length of the nest building to brood rearing period were consistent with reports on wild birds. Males and females spent approximately the same amount of time for each reproductive behavior. Notably, we documented, for the first time, that pairs made second breeding attempts in the same year, showing that this species is physiologically capable of reproducing twice in the same year. The second breeding attempt began after the first brood fledged, but its progress was disturbed by interactions with the fledglings from the first clutch.

The Spotted Nutcracker Nucifraga caryocatactes feeds on and hoards the seeds of trees in the genus Pinus. Although its hoarding behavior is easy to observe in the open alpine zone, its main habitat is the dense subalpine zone where their behavior has not been studied in detail. In this study, we surveyed the species' feeding and hoarding behavior to better understand its preferred hoarding locations in the subalpine zone. We focused on the seeds steal by competing species and the effects of snow cover. Our results show that the Spotted Nutcracker hoards seeds in areas of bare earth, in patchy plant communities and forests, with a high hoarding tendency in forest in September and in patchy plant communities in October and November. Nutcrackers did not cache seeds randomly, but rather in locations that were less susceptible to seed theft by competitors and less susceptible to snow accumulation.