We aimed to calculate the annual survival rates of male Ryukyu Scops Owl Otus elegans on eight islands, Nakano-shima (NKN), Amami-oshima (AMM), Tokuno-shima (TKN), Izena (IZN), Iheya (IHY), Ishigaki (ISG), Iriomote (IRO) and Hateruma (HTR), in the Ryukyu Archipelago, and to discuss the environmental factors that cause differences in their annual survival rates. A total of 111 owls was marked (19 on NKN, 19 on AMM, 11 on TKN, seven on IHY, four and six on IZN, 14 on ISG, 20 on IRO and 11 on HTR) between March and July from 2011 to 2016. We investigated whether they were resighted at the same sites at different annual intervals on each island in February, June-October, and December from 2016 to 2023. To calculate survival rates from unequal interval observations, we used a model that relaxed the assumptions of the Cormack-Jolly-Seber model, which calculates survival rates from equal intervals. The mean annual survival rate for all eight islands was 80.1% with a credible interval of 68.0% to 91.7%. The mean annual survival rates for IHY (87.0%), AMM (79.8%) and NKN (88.2%) were within the credible interval for the mean survival rate for all islands, although the credible interval for IHY tended to be larger than that for the other two islands. The annual survival rates for IZN (50.2%) and TKN (49.9%) were remarkably lower than those for the other six islands, although with very large credible intervals. The mean annual survival rate for HTR (96.3%), IRO (91.5%) and ISG (97.9%) tended to be high compared to that for all the other islands. Estimates of annual survival indicate that there may be differences in owl survival rates between islands. The results suggest that annual survival rates vary depending on island environments. This study highlights the biological evolutionary importance of comparing differences in traits of Ryukyu Scops Owl among islands.

To examine the value of tongue spots as a tool for determining the age-class of Lanceolated (LGW), Middendorff's (MGW), and Sakhalin Grasshopper warblers (SGW), interspecific and individual differences in tongue spots were inspected during the breeding seasons from 2020 to 2023 in Hokkaido. A subjective tongue spot scoring system (TSS) was used. A score of TSS 1 indicates black is very light and barely visible; TSS 2 indicates that the spots have an indistinct outline and are light black; while TSS 3 indicates that spots have clear outlines and are dark black. The tongue spots of a pair of LGW differed, the male was TSS 3 and the female TSS 1. The male TSS 3 was comparable to the most distinct juvenile MGW. Tongue spots in LGW are suitable for age-class determination. Out of 40 adult SGWs, 22.5% were classified as TSS 1, 70% as TSS 2 and 7.5% as TSS 3. Out of 149 adult MGWs, 72.5% were classified as TSS 1, and 27.5% as TSS 2; none were TSS 3. TSS did not change between successive years in SGW or MGW, making it impossible to determine their age classes. A possible significance of tongue spots as a signal of physiological condition was investigated in juvenile MGWs. Of the 41 juvenile MGWs, 12.2% were classified as TSS 1, 48.8% as TSS 2 and 39% as TSS 3. Juveniles with TSS 2 had shorter wings and longer tails than those with TSS 1. This inconsistency means that the process of fading of tongue spots is not simply the result of ageing. There were individual differences in TSS within the same brood in the same nest. We assumed that dark tongue spots of juvenile MGWs were a signal of their good physiological condition.

Studies of geographic variation aid advanced taxonomy as well as the understanding of microevolutionary forces, speciation, and the nature of species and biodiversity. This emphasizes the need to review the understanding of geographic variation in avian species that was developed primarily from the viewpoint of species classification. The main purpose of this study was to examine geographic variation in the body size of Black-headed Gull Chroicocephalus ridibundus, a monotypic species. Our dataset consisted of measurements of 70 skin specimens of adult Black-headed Gull from museum collections. Morphological measurements of tarsus length, total head length, entire bill length, nalospi length, and bill depth at the gonys were used for statistical analyses. Morphological measurements were compared among breeding areas of the Black-headed Gull across the entire Palearctic region. Those breeding on the Kamchatka Peninsula, Russian Far East, were significantly larger (especially for total head length and nalospi length) than those of other Palearctic breeding populations. A west to east increasing trend in size was also observed. In addition, birds wintering in Japan were revealed to be mainly from the Kamchatka breeding population, based on body size measurements. The recovery records of birds banded in the Russian Far East support this finding.

Using a standardized method to track long-term fluctuations in avian populations is important for proposing effective conservation strategies for birds. From 2013 to 2022, we conducted constant-effort mist netting and bird banding during the breeding season in a lowland deciduous forest in western Hokkaido, Japan. A total of 1,327 individuals of 30 species were banded or recaptured. Twenty-four species bred in the study area, two species periodically passed through the site, and four species were considered accidental visitors. Breeding adult Asian Stubtail Urosphena squameiceps and Eastern Crowned Leaf Warbler Phylloscopus coronatus declined significantly during the study period, although, there was no decline in their rate of reproduction. In the absence of forest deterioration, this suggests that their declines may have resulted from environmental changes along their migration routes or on their wintering grounds. Significantly more adult male Asian Stubtail than females were captured annually. This was assumed to be because of the unique breeding habits of this species. The recapture probabilities (p) of males were higher than those of females in four species (Asian Stubtail, Eastern Crowned Leaf Warbler, Japanese Thrush Turdus cardis, and Black-faced Bunting Emberiza spodocephala), but vice versa in Narcissus Flycatcher Ficedula narcissina. Among these five species, the adult apparent survival rate (φ) was highest for Black-faced Bunting and lowest for Eastern Crowned Leaf Warbler. The number of sites comparing the vital indices of birds in Japan should be increased in the future, as in the Constant Effort Sites (CES) ringing scheme in Europe and the Monitoring Avian Productivity and Survivorship (MAPS) program in North America.

Bird banding, a valuable survey method for understanding avian biology, can be applied to the conservation of endangered species. In this study, a banding survey of the endangered Amami Woodcock Scolopax mira, which is endemic to the Ryukyu Archipelago in southwestern Japan, was conducted to accumulate fundamental ecological data. This species is frequently observed on forest roads at night; therefore, banding was conducted concurrently with a nighttime monitoring survey performed via a motor vehicle census. Over the 17-year study period, 704 individuals were captured and marked, of which 258 individuals (37%) were resighted. The average interval between marking and resighting was less than one year, with only 14 individuals (5%) resighted after more than three years. The low resighting rate may reflect the species' short lifespan, but it is plausible that fewer individuals appear on the road over time, with resighted individuals representing a small fraction of the population. Distances between marked and resighted points were calculated for 119 individuals, revealing an average distance of 548 m, indicating the species' notable site fidelity. However, some individuals were occasionally observed on islands further south within the archipelago during the non-breeding season, suggesting that the species exhibits partial migration, although the ecological significance of this behavior remains unclear. Banding can play a crucial role in efforts to conserve the Amami Woodcock population; therefore, we intend to continue this banding survey to contribute further essential data for the species' conservation.

Bird-banding surveys are a long-established method for revealing aspects of bird migration. However, this method is often criticized for its bias in recovery or resighting locations owing to the uneven distribution of observers, and its reliance on opportunistic observations. In this study, we examined the seasonal and local movement of Black-headed Gull wintering in Japan by analyzing banding and resighting records of marked individuals, combined with morphological measurements from three wintering areas. Between 1978/79 and 2020/21, a total of 2,370 gulls were marked in Kanto, Kansai, and Kyushu. A total of 7,885 resighting records of 1,229 individuals were obtained from 1981/82 to 2022/23. The wintering populations in Kanto and Kansai were confirmed to summer on the Kamchatka Peninsula and in East Siberia, with their migration routes passing through eastern Hokkaido and along the Pacific coast of Honshu in autumn and spring. In contrast, individuals banded in Kyushu were resighted on the Korean Peninsula. Morphological measurements of these wintering populations, revealed that body size was larger in the Kanto population than in the Kyushu population. Since Black-headed Gull exhibits geographic variation in body size, it can be inferred that the wintering populations in Kanto and Kyushu originate from different breeding grounds. The Kansai population was intermediate, with no difference in body size compared with the Kanto and Kyushu populations and no distinct peaks in distribution of body size variation, indicating that it consisted of birds mixing from multiple breeding grounds. Differences in seasonal movements detected by banding/resighting records were supported by body size variation among the three areas. Black-headed Gull wintering in Japan appear to be derived from multiple breeding populations with different body size, and with the proportion of individuals from different breeding populations varying among wintering areas.

Bird banding has been widely used for more than a century to study the large-scale spatial movements of birds. Continent-wide and transcontinental movements of birds, such as dispersal and seasonal migration, have been revealed by ring recoveries that link departure and destination locations. However, movement inferences have been mostly qualitative, and many limitations and biases have impeded accurate and detailed inferences of movement patterns. Banding data, nevertheless, provides the largest data set for bird movement studies, thus the development of statistical methods to utilize them effectively is the active frontier of research. In this review, we summarize briefly emerging opportunities for quantitative inferences of bird movements from banding data and indicate how they have improved our understanding of bird movements. Banding data is powerful when integrated with external data sources (e.g., direct tracking data), and prove informative for macroecological and macroevolutionary studies. However, such integrated practices have been limited to studies of European and American avian species. A systematic review of the use of Japanese banding data in scientific publications, shows that it is used significantly less often than that of European or American data, and publications were often invisible to the international scientific community. This poor visibility and low rate of usage is likely due to the relative inaccessibility of the data, as most of it is published in Japanese, and the relatively small number of ring recoveries, which makes the data less attractive. We argue that such an inter-flyway disparity may have created severe knowledge gaps in avian movement studies, including incorrect predictions of avian responses to future climate change and less effective conservation actions in Asia. The Japanese data represents Asia's largest banding and recovery archive, and future work needs to effectively integrate it into cutting-edge statistical frameworks to expand the field of bird movement studies.

Non-native bird species have colonized and negatively affected natural ecosystems and social economics globally; however, most cases have been poorly studied. We evaluated the effectiveness of playback surveys for enhancing detectability of the non-native Red-billed Blue Magpie Urocissa erythrorhyncha, and revealed the drivers of the magpie's distribution using an occupancy model that considers the detection process and effects of survey conditions in Shikoku, southern Japan. Using this model, we mapped the potential distribution of suitable magpie habitats across Shikoku. Furthermore, we obtained detection/non-detection data for native bird species (Narcissus Flycatcher Ficedula narcissina, Varied Tit Poecile varius, Japanese Tit Parus minor, and Japanese Bush Warbler Cettia diphone), and evaluated the impacts of magpie presence on occupancy of these native bird species using a multispecies occupancy model that considered interspecific interactions (i.e., co-occurrence or mutually exclusive occurrence patterns). The results showed that detection probability was enhanced by broadcasting a specific series of magpie calls in the early morning from late May to early July. Magpie occupancy was higher in areas of lower elevation and peaked in areas with moderate forest cover (76%). However, magpie presence did not significantly affect the occupancy of four native bird species. Mapping the distribution of magpie occupancy demonstrated that potentially suitable habitats are widely distributed in near-coast areas between lowlands and mountains, even in eastern Shikoku, which has not yet been colonized. Therefore, before the magpie expands across Shikoku and becomes prevalent, it will be necessary to further assess potential impacts of magpies on local native species, develop efficient methods to capture magpies, and establish a monitoring scheme in priority areas to block magpie expansion. Our approach, using a combination of playback surveys and models considering detectability, holds potential for application in studies of other non-native bird species, as well as to support their appropriate management.

Seasonal and inter-annual changes in the diets of seabirds are expected to relate to the abundance and distribution of their prey species. We analyzed the stomach contents of 227 male and female Streaked Shearwater Calonectris leucomelas during the chick-rearing period on Awashima in the Sea of Japan between 2008 and 2013. They fed predominantly on Japanese Anchovy Engraulis japonicus early in the season but changed their diet, consuming increasing numbers of benthic fish species (mainly Gadidae, Sebastidae, and Zoarcidae) later in the season. Being surface feeders, they possibly fed on these benthic species discarded by the trawl fishing boats in intense fishing grounds of both the Pacific and the Sea of Japan. Moreover, the shearwaters also showed sex-specific differences in their diet. Females fed more on anchovies, while males tended to feed more on benthic species, presumably when they fed in the Pacific and the northern part of the Sea of Japan. They fed more on benthic fish in years with high sea surface temperatures (SST), probably due to low availability of epipelagic fish. With the trend of global sea warming, our results indicate the importance of fisheries-related food sources far from the colony for this generalist surface-feeding seabird.

Habitat selection by Chestnut-cheeked Starlings Agropsar philippensis was studied in Morioka City, Iwate Prefecture, Japan. The location and numbers of Chestnut-cheeked Starling and White-cheeked Starling Spodiopsar cineraceus were recorded along one-kilometer-long transects in 172 survey plots during May, June and July 2022. Chestnut-cheeked Starlings were observed from early May to early July. Multiple comparison tests indicated that significantly more individuals were observed in urban areas, farmland, and urban/farmland areas, than in forests. From the results of Generalized Linear Model (GLM) analysis, the best model that considered urban areas, rice fields, and other agricultural areas, was considered optimal for the species. The model that considered urban areas, rice fields, other agricultural areas, and rivers was also selected as a useful model. For White-cheeked Starlings, the model that considered urban areas, rice fields, other agricultural areas, and rivers was selected. Our results showed that the two species have discontiguous distributions — Chestnut-cheeked Starling has a strong preference for urban areas, whereas White-cheeked Starling prefers farmland areas. Since Chestnut-cheeked Starlings inhabit areas that are in close proximity to humans, human activity likely has a significant impact on them.

Microplastics ingested by seabirds may decrease digestive ability, increase stress levels, and cause lesions in their digestive tracts. Hazardous chemicals added to and accumulated in these plastics may also pose adverse effects. To examine these effects, two experiments were carried out using wild Streaked Shearwater Calonectris leucomelas chicks. We dosed them orally with either 0.43 g plastic pellets with chemical additives (flame retardant and UV stabilizer), or 2.00, 3.00 and 4.00 g virgin plastic pellets without additives. The dose of pellet loads of up to 0.8% of chick body mass did not affect growth in body mass, structural size, meal mass per day, or plasma stress hormone levels. Pellets with chemical additives, however, appeared to adversely affect liver and kidney masses during their early development, raising the concern of potential toxic effects of chemical additives within the microplastics themselves, in the stomachs of seabirds.

Although the neck plumage of crows appears mostly black, it can look green or blue when observed carefully. In this study, we examined the neck feather coloration of 55 Large-billed Crow Corvus macrorhynchos and 32 Carrion Crow Corvus corone captured in Tochigi and Kanagawa prefectures. Visual observation revealed that most Large-billed Crow had green, teal, or blue neck feathers, whereas most Carrion Crow had blue neck feathers. The reflectance spectra, brightness (L*), and chromaticity (a* and b*) were measured at three regions of the neck of each crow by spectroradiometer. Peak reflection occurred at 480.4 ± 32.5 nm for Large-billed Crow and 422.6 ± 15.3 nm for Carrion Crows, and the difference between species was significant. A scatter plot of chromaticity showed a strong correlation only in Carrion Crow. An analysis of covariance was performed to examine the difference in the correlation between a* and b*, and a significant species difference was found. The plots of Large-billed Crow distributed on the left side of the scatter plot comparing with the regression line of Carrion Crow. These results suggest that there is a species-specific difference between the neck feather coloration of these two species, with Large-billed Crow feathers varying from green to blue, whereas those of Carrion Crow were only blue. Further research is required to reveal the specific features of neck plumage color variation in crows, especially in order to understand the variation among individual Large-billed Crow.

Transmitter-based bird tracking is crucial in modern ecology and conservation biology. This type of research provides fundamental insights into avian movement patterns, habitat utilization, areas of intense activity, and migration routes. In this study, we tracked the spring migration routes of nine Baikal Teal Sibirionetta formosa equipped with platform transmitter terminals (PTTs) and revealed three main migration routes (MR1, MR2 and MR3) from South Korea to their breeding grounds in Russia. Although most birds bred in the Kolyma Lowland, some bred along the lower reaches of the Lena River. Furthermore, it was confirmed that migratory birds used 25 stopovers. Notably, a route (MR1) passing through northeastern China, eastern Russia, and the Sea of Okhotsk was utilized by most Baikal Teal and corresponded with the well-known route identified in Japan. Two other migration routes (MR2 and MR3) shared a common path from western regions of South Korea to wetlands located west of Heilongjiang Province, China. From the Recka Gonam River basin in Russia, one migration route turned northeastward towards the Kolyma Lowland, whereas the other continued northward to the lower reaches of the Lena River. These routes were supplementary migration routes that extend beyond the previously known migration routes of Baikal Teal. This study contributes to the current understanding of Baikal Teal migration patterns and identifies areas that should be prioritized for conservation efforts.