In order to understand the diet of Laysan Albatross Phoebastria immutabilis and Black-footed Albatross P. nigripes in western North Pacific waters, we investigated isotopic differences between species, sexes and breeding stages. We measured carbon and nitrogen isotope ratios in the muscles and livers of albatrosses (caught during Japanese pelagic longline fishing) and in their potential prey. Both δ¹³C and δ¹⁵N of Black-footed Albatross were higher than those of Laysan Albatross. Delta¹³C of both species differed seasonally and δ¹³C was lower during the incubation period than during the chick-provisioning and non-breeding periods. The δ¹³C and δ¹⁵N levels of males did not differ from those of females in either species. Our results suggest that Black-footed Albatross forages on higher isotope prey items and/or Laysan Albatross forages on lower isotope prey items other than squid and fish and that δ¹³C varies in response to seasonal variation in prey availability. This implies that Black-footed Albatross forages more on discard from the fishing industry than does Laysan Albatross; this in turn may be related to the areas of operation sea area of the longline fisheries in the western North Pacific. In conclusion, it is important for conservation of these two albatross species to monitor their diets and foraging areas and to identify the species-specific high-risk areas where albatross bycatch is most likely.

The White-browed Guan Penelope jacucaca is an endangered member of the family Cracidae endemic to the Caatinga region of northeast Brazil. Hunting and habitat loss are the presumed major threats to the species, however, their impacts on its occurrence have been insufficiently tested. We used field observations and information on hunting activity to assess whether hunting, landscape and/or climate affect the occurrence of the White-browed Guan in the Caatinga. We sampled 23 localities within the Caatinga and recorded the species' occurrence and hunting encounters. For each locality, we extracted three landscape metrics (vegetation cover, patch aggregation, and patch richness); two climate variables (temperature seasonality and mean precipitation of the wettest month); and one topographic variable (mean slope). We then used generalized linear models based on proportion to determine if the species' occurrence was related to these environmental factors. We found a greater likelihood of detecting the species in localities with greater slope, greater heterogeneity of habitats and more stable temperatures, whereas hunting activity presented a trend of negative impact on occurrence. Our results emphasize the relevance of using different environmental metrics to implement conservation programs for this threatened species.

Empirical ornithologists often analyse dispersal distance by histograms separately drawn for categories of individuals (e.g., sexes), and/or by linear models with normal distribution (e.g., ANOVA). However, theoreticians describe dispersal distance by dispersal kernels with various parametric distributions. Therefore, it is a helpful exercise for empiricists to estimate dispersal kernels from field data. As a model case for such an estimation, we analysed dispersal data of the Ryukyu Scops Owls Otus elegans using a Bayesian Weibull regression model. Estimated dispersal kernels showed that males and individuals fledged from late-breeding nests had short natal dispersal distances and that no factors affected breeding dispersal significantly.

In this study we investigated the eye morphology and retinal topography of two owl species in relation to their visual environment. Although Short-eared Owl Asio flammeus is larger and weighs more than Japanese Scops Owl Otus semitorques, its eye dimensions (weight, corneal diameter, and axial length) are all smaller than the scops owl's. Owl retinas were examined in Nissl-stained whole-mount preparations. The total number of retinal ganglion cells (RGCs) was greater in the Japanese Scops Owl (4,703.0×10³ cells) than in the Short-eared Owl (2,346.8×10³ cells). The eye morphology of, and the number of RGCs in the Japanese Scops Owl indicate that it is more adapted to a nocturnal habit. An area of high-density RGCs was horizontally distributed in the temporal retina of the Short-eared Owl, with a peak density of 17.4×10³ cells/mm². In the Japanese Scops Owl's temporal retina, there was an oval-shaped arrangement with a peak density of 23.1×10³ cells/mm². These distributions indicate that whereas Short-eared Owl is adapted to open habitats, Japanese Scops Owl is adapted to enclosed habitats. The RGCs of both species were classified into three categories (small, medium, and large) based on the size and appearance of somas. In both species, medium-sized cells predominated, and the proportion of large-sized cells was smallest. The distribution and high-density areas differed among these groups, suggesting adaptation to the visual environment. The high-density areas of these groups cover the nasal visual fields, which include the overlap for binocular vision.

Negative relationships between the degree of parental investment and the presence of unrelated offspring in the nest due to extra-pair paternity (EPP) or conspecific brood parasitism (CBP) are predicted in monogamous species. This is because investing in unrelated offspring is costly to individual parents. However, such strategies may be adaptive for one social partner. Because parental investment changes in response to that by the social partner, the predicted relationship needs to be assessed empirically in wild animal populations, with consideration for male and female parental care. Furthermore, both EPP and CBP must be considered simultaneously in such a study. In this study, we tackled the issue using the semi-colonial Eurasian Tree Sparrow Passer montanus, in which both EPP and CBP were predicted to occur. We tested whether there is a negative relationship between the degree of parental care of both males and females and the presence of EPP or CBP, taking into consideration the parental investment of their social partners, using behavioral observations and parentage analyses based on seven microsatellite loci. The results revealed a moderately high frequency of EPP and CBP within a sparrow colony. A negative relationship between parental care by the social male parent and the presence of EPP was suggested, while this was possibly as a result of the increase in parental investment by their female partner. CBP was also inferred to be linked with male parental investment, while females may have compensated for the cost of CBP in their provisioning efforts by egg rejection. High frequencies of occurrence of both EPP and CBP allowed us to shed light on how parental investment is related to the presence of unrelated young in the complex social system of the Eurasian Tree Sparrow.

Pheasants remain among the least studied but most popular species targeted by hunters and trappers in many parts of Nepal. Cheer Pheasant Catreus wallichii, is classified as rare and Vulnerable by the International Union for Conservation of Nature, an Endangered species in the National Red List of Birds in Nepal, and one of nine protected priority bird species of Nepal. Despite its global and national significance, it has been declining in Nepal, and in other parts of its range. Snaring and hunting are the main causes for its decline in Nepal. Furthermore, scientific research and conservation efforts for the Cheer Pheasant have been focused on a few Protected Areas (PAs), ignoring the large areas of its range that lie outside the PAs system. Despite the species' occurrence being reported opportunistically, no fieldwork focusing on Cheer Pheasant has been carried out in Far-Western Nepal. Therefore, from 2014 to 2016, a survey and informal interviews were conducted in Baitadi, Achham and Bajura districts of Far-Western Nepal to learn more about the species' status, distribution, and conservation challenges. As a result of this work, Cheer Pheasant has been found in new locations in Nepal, including Pancheshwor Rural Municipality in Baitadi, Mangalsen Municipality in Achham and Badimalika Municipality in Bajura District. The main anthropogenic threats to the species in Far-Western Nepal include trapping, shooting, egg collection, and forest fire. The species has already disappeared from some locations where local people observed them frequently in the past. Therefore, intensive study of the relationship between Cheer Pheasant and underlying threats is necessary. Additionally, conservation campaigns should be focused on hunting groups and local people, as awareness in the region is poor.

Inspired by ecologists R. H. MacArthur and E. O. Wilson, who pioneered the use of islands as ideal model systems for researching the formation and maintenance of biodiversity, we studied two sympatric passerine bird species on a volcanic archipelago, in Japan. We focused on the occupancy and co-occurrence of Varied Tit Sittiparus varius and Cinereous Tit Parus cinereus, both members of the Parus guild, on the Izu Islands. Their populations range from being stable, and co-occurring, to being temporally unstable (with local extinctions, invasions, and species replacement) and even totally absent. Using results from several surveys carried out on the islands over the last 60 years, and our own contemporary surveys, we tested the ecological drivers of inter-island occupancy through occasional dispersal of these two species. We found that both species had positive relationships with island size and vegetation diversity, while Cinereous Tit exhibited a negative associating with distance to the mainland (Honshu, Japan). Cinereous Tit was also negatively correlated with Varied Tit, but their co-occurrence was positively associated with island size, connectivity, and vegetation diversity. We suspect that resource constraints play a significant role in the distributions of the two species on the islands. Varied Tit is dominant over Cinereous Tit, but Cinereous Tit is able to utilize a wider range of habitats and resources. We also discuss the potential for a competition-colonization trade-off for the two species on the islands.

Our study provides the first GPS tracking data of Little Egret Egretta garzetta from an East Asian population. Our two main objectives were to reveal the migratory route and migratory strategy of Little Egret, and to study inter-annual breeding and wintering site fidelity. Our data, from an adult and a juvenile, suggest that this species is a short-distance high-speed migrant using few or no stopover sites. Both individuals displayed high breeding and wintering site fidelity. They also used very small winter home ranges, probably associated with high prey availability in aquaculture ponds.

We used radio telemetry to provide the first information concerning home range size of Hainan Partridge Arborophila ardens, a vulnerable species endemic to Hainan Island, China, in both a fragmented and a continuous natural rainforest. Both the monthly and daily home range sizes of the population in the fragmented rainforest were significantly larger than those in the continuous rainforest, with no difference between males and females. Fragmentation reduced habitat quality and thus may have forced the partridges to forage over a wider range, which may threaten their survival.

On 13 June 2021, a video was recorded showing an adult female Asian Koel Eudynamys scolopaceus removing three Elliot's Laughingthrush Trochalopteron elliotii nestlings from a nest in a thicket on the banks of Liqiu River in Xinduqiao Town, Kangding, Sichuan, Southwestern China. This is the first record of an Asian Koel removing nestlings from a potential host's nest. Of the various brood parasitism hypotheses, this behavior is most consistent with the farming hypothesis, further suggesting that farming behavior may be a common strategy used by obligate brood parasites.

We describe, for the first time, the rattling call of the Crested Honey Buzzard Pernis ptilorhynchus. This was previously considered to be a unique vocalization of European Honey Buzzard Pernis apivorus; however, we detected this series of rapidly repeated notes given by an adult female, a second-year, a juvenile and a nestling Crested Honey Buzzard. The rattling calls appeared to be given at times of great excitement, such as to an approaching intruder, mate or parent at the nest, or to a familiar person who usually gave food in the case of captive individuals. The rattling call of an adult female Crested Honey Buzzard at the nest was at a frequency of 2.12 (s.d.±0.07) kHz, and lasted 141 (s.d.±18) ms, which was higher and longer than in European Honey Buzzard.