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Simple Summary: Our comprehensive study using camera traps in the Halla Mountain Wetland offers significant insights into the temporal activities and habitat preferences of Passerine birds. Key findings include distinct morning activities in species such as Cyanoptila cyanomelana and Horornis canturians and afternoon peaks in others such as Muscicapa dauurica. We observed a preference for wetlands and an underutilization of grasslands, indicating complex species–habitat interactions. Additionally, our study highlights the impact of population density on habitat usage and reveals substantial variations in seasonal activity among different species, demonstrating their adaptive strategies. This research contributes to a deeper understanding of the ecological dynamics and niche partitioning within these bird communities. However, the fixed field of view and intermittent recording capability of camera traps can miss certain activities, and external factors such as weather and human presence can influence the observed behavior. While providing valuable insights, this study underscores the need to integrate camera trap data with other observational methods for a more comprehensive understanding of avian behavior. This study analyzed 5322 camera trap photographs from Halla Mountain Wetland, documenting 1427 independent bird sightings of 26 families and 49 species of Passeriformes. Key observations include morning activities in Cyanoptila cyanomelana and Horornis canturians and afternoon activity in Muscicapa dauurica and Phoenicurus auroreus. Wetlands were significantly preferred (P_i = 0.398) despite their smaller area, contrasting with underutilized grasslands (P_i = 0.181). Seasonal activity variations were notable, with overlap coefficients ranging from 0.08 to 0.81 across species, indicating diverse strategies in resource utilization and thermoregulation. Population density was found to be a critical factor in habitat usage, with high-density species showing more consistent activity patterns. The study's results demonstrate the ecological adaptability of Passeriformes in the Halla Mountain Wetland while highlighting the limitations of camera trapping methods. These limitations include their fixed field of view and intermittent recording capability, which may not fully capture the spectrum of complex avian behaviors. This research underlines the need for future studies integrating various methodologies, such as direct observation and acoustic monitoring, to gain a more comprehensive understanding of avian ecology. [ABSTRACT FROM AUTHOR]

Echolocating bats emit echolocation calls from the mouth or nose. Bats that emit calls from the nose have oddly developed dome-shaped nasal bones, but variations in the morphology of these bones are poorly understood. This study compared trends in the morphological variations of the cranium focusing on smooth structure such as the nasal swellings and the braincase, and investigated the morphological variability correlated with ultrasound vocalizations. We newly constructed three-dimensional (3-D) skull mesh models of the two Japanese rhinolophid species Rhinolophus nippon and Rhinolophus cornutus from the Korean Peninsula, the Japanese Archipelago, and Jeju Island, and compared the variations in cranium size and shape using 3-D geometric morphometrics. Additionally, we also tested trends in two representative body size indices, forearm length and centroid size. The results indicate that forearm length and log-transformed centroid size represented different trends among local populations. The results of 3-D geometric morphometrics show a significant difference in cranium shape between the two species, and between the Jeju Island population and the Japanese mainland population of R. nippon, indicating variability in the pair of nasal swellings related to nasophonation of the echolocation call. The anterior median swelling varied within the R. nippon populations, and the posterior median swelling varied between R. nippon and R. cornutus. These findings suggest that the variability between the anterior median swelling creates different echolocation peak frequencies in local populations, and that the posterior median swellings are quite similar among local populations because of the strong functional constraint of diet and echolocation. [ABSTRACT FROM AUTHOR]

Analysis of spatiotemporal partitioning is pivotal to shed light on interspecific coexistence. Most research efforts have involved large-sized carnivores and their prey species, whereas little attention has been given to ungulate in the predator-free ecosystems. We assessed seasonal activity patterns and spatiotemporal overlap among the Siberian roe deer (Capreolus pygargus tianschanicus) and its sympatric species through camera-trapping from October 2017 and September 2020 in Jeju Island, South Korea. Trap events when compared seasonally, roe deer show higher activity in summer (34.9%), a pronounced low in winter (14.1%), and a moderate in autumn (23.8%) and in spring (26.9%). Roe deer exhibited bimodal activity patterns and had the highest spatiotemporal overlap and composite score with sika deer (Cervus nippon). Our results are among the few available data on the interaction of sympatric species and suggest strong overlapping with sika deer. This study provides important insight into species coexistence in predator-free habitats, which would be important for management initiatives. [ABSTRACT FROM AUTHOR]