摘要: Birds, a fascinating and diverse group occupying various habitats worldwide, exhibit a wide range of life-history traits, reproductive methods, and migratory behaviors, all of which influence their immune systems. The association between major histocompatibility complex(MHC) genes and certain ecological factors in response to pathogen selection has been extensively studied; however, the role of the co-working molecule T cell receptor(TCR) remains poorly understood. This study aimed to analyze the copy numbers of TCR-V genes, the selection pressure(ω value) on MHC genes using available genomic data, and their potential ecological correlates across 93 species from 13 orders. The study was conducted using the publicly available genome data of birds. Our findings suggested that phylogeny influences the variability in TCR-V gene copy numbers and MHC selection pressure. The phylogenetic generalized least squares regression model revealed that TCR-Vαδ copy number and MHC-I selection pressure were positively associated with body mass. Clutch size was correlated with MHC selection pressure, and Migration was correlated with TCR-Vβ copy number. Further analyses revealed that the TCR-Vβ copy number was positively correlated with MHC-IIB selection pressure, while the TCR-Vγ copy number was negatively correlated with MHC-I peptide-binding region selection pressure. Our findings suggest that TCR-V diversity is significant in adaptive evolution and is related to species' life-history strategies and immunological defenses and provide valuable insights into the mechanisms underlying TCR-V gene duplication and MHC selection in avian species.

摘要: Birds exhibit a high degree of migratory diversity, which is influenced by various ecological factors and life history strategies. Conducting studies on tropical bird migration, of which research is scarce, and comparing it with temperate birds can enhance our understanding of bird migration behaviour and its underlying mechanisms. In this study, we explored the migration behaviour of a breeding population of the Barn Swallow(Hirundo rustica) in Zhanjiang, southern China, a region located in the northern tropics, using light-level geolocators. From 2021 to 2023, we deployed geolocators on 92 breeding swallows and retrieved geolocators successfully from 23 individuals. These swallows all exhibited migratory behaviour, and wintering on various islands in Southeast Asia. They displayed sex differences in their wintering locations. All males concentrated in Borneo, while females primarily chose Borneo but also dispersed to the Philippines, South China Sea, and Vietnam for wintering. The studied swallow population adopted a seasonal migration pattern of “indirect in autumn, direct in spring”, bypassing the ecological barrier of the South China Sea in autumn and tending to directly cross it in spring migration. Moreover, the distance and duration of autumn migration was significantly longer than those of the spring migration. Compared to temperate Barn Swallows, the Barn Swallow population breeding in Zhanjiang adopts a pattern of “intra-tropical migration” and initiates autumn migration earlier. The formation of their migration pattern may be limited by ecological and physiological factors.

摘要: Many migratory birds exhibit interannual consistency in migration schedules, routes and stopover sites. Detecting the interannual consistency in spatiotemporal characteristics helps understand the maintenance of migration and enables the implementation of targeted conservation measures. We tracked the migration of Whimbrel(Numenius phaeopus) in the East Asian–Australasian Flyway and collected spatiotemporal data from individuals that were tracked for at least two years. Wilcoxon non-parametric tests were used to compare the interannual variations in the dates of departure from and arrival at breeding/nonbreeding sites, and the interannual variation in the longitudes when the same individual across the same latitudes. Whimbrels exhibited a high degree of consistency in the use of breeding, nonbreeding, and stopover sites between years. The variation of arrival dates at nonbreeding sites was significantly larger than that of the departure dates from nonbreeding and breeding sites. Repeatedly used stopover sites by the same individuals in multiple years were concentrated in the Yellow Sea coast during northward migration, but were more widespread during southward migration. The stopover duration at repeatedly used sites was significantly longer than that at sites used only once. When flying across the Yellow Sea, Whimbrels breeding in Sakha(Yakutia) exhibited the highest consistency in migration routes in both autumn and spring. Moreover, the consistency in migration routes of Yakutia breeding birds was generally higher than that of birds breeding in Chukotka. Our results suggest that the northward migration schedule of the Whimbrels is mainly controlled by endogenous factors, while the southward migration schedule is less affected by endogenous factors. The repeated use of stopover sites in the Yellow Sea coast suggests this region is important for the migration of Whimbrel, and thus has high conservation value.

摘要: Seabirds are valuable indicators of marine ecosystem processes and studying seabird diets can shed light on natural or human-induced variability in food-web composition. Specifically single-prey loading seabird species such as terns have the potential to act as visual sentinels of prey availability offshore. However, obtaining diet information from remote bird colonies is often challenging and time consuming. In this pilot study we present a novel approach to combine two established methods to study seabird foraging ecology, providing a powerful and cost-effective tool to study the distribution of prey items available to seabirds. We combined GPS tracking data of Sandwich Terns(Thalasseus sandvicensis) with prey-observations from a hide in 2012 and 2013, and from semicontinuously recorded camera footage in 2017. By doing so, we identified 115 approximate catch locations of prey(86 herring/sprat Clupeidae, 29 sandeel Ammodytidae). Combining GPS-data and prey observations yielded detailed knowledge on the movements and chick diets of tracked birds as well as the spatial origin and lengths of captured prey items. Further catch distances of both Clupeidae and Ammodytidae resulted in deliveries of larger prey items and thus higher energy yield per trip, but also a higher energy expenditure per trip. We discuss the limitations and potential of our methodological approach to study foraging energetics during chick-provisioning of seabirds that carry prey items visible in their beaks.

摘要: Individuals may gather information about environmental conditions when deciding where to breed in order to maximize their lifetime fitness. They can obtain social information by observing conspecifics and heterospecifics with similar ecological needs. Many studies have shown that birds can rely on social information to select their nest sites. The location of active nests and the reproductive success of conspecifics and heterospecifics can provide accurate predictions about the quality of the breeding habitat. Some short-lived species can facultatively reproduce two and/or more times within a breeding season. However, few studies have focused on how multiplebrooding individuals select nest sites for their second breeding attempts. In this study, we use long-term data to test whether the Japanese Tit(Parus minor) can use social information from conspecifics and/or heterospecifics(the Eurasian Nuthatch Sitta europaea, the Daurian Redstart Phoenicurus auroreus and the Yellow-rumped Flycatcher Ficedula zanthopygia) to select a nest site for the second breeding attempt. Our results showed that the nest boxes occupied by tits on their second breeding attempt tended to be surrounded by more breeding conspecific nests, successful first nests of conspecifics, and fewer failed first nests of conspecifics than the nest boxes that remained unoccupied(the control group). However, the numbers of breeding heterospecific nests,successful heterospecific nests, and failed heterospecific nests did not differ between the nest boxes occupied by tits on their second breeding attempt and the unoccupied nest boxes. Furthermore, the tits with local successful breeding experience tended to choose areas with more successful first nests of conspecifics than those without successful breeding experience. Thus, we suggest that conspecifics' but not heterospecifics' social information within the same breeding season is the major factor influencing the nest site selection of Japanese Tits during second breeding attempts.

摘要: As the sole obligate symbiotic birds in Africa, oxpeckers offer a unique model for studying symbiotic relationships. Due to the multitrophic level they occupy and the context dependent foraging behavior they exhibit, the type of symbiotic relationship can be variable. In addition to providing a cleaning service to the host by removing ticks, oxpeckers frequently feed on blood, mucus, and saliva, inflicting potential damage on the host. Here, we used DNA metabarcoding on faecal samples to analyze the taxonomic composition of the trophic interactions of the Yellow-billed Oxpecker(Buphagus africanus) and Red-billed Oxpecker(B. erythrorhynchus) in northeastern Namibia. In contrast to conventional methods, DNA metabarcoding allows for a detailed identification of dietary resources encompassing both mammal hosts and consumed arthropods within the same samples. With this information, we examined differences in the diet composition between oxpecker species and localities, as well as the co-occurrence between host and arthropod species. Our findings revealed that oxpeckers predominantly source their diet from mammals, ticks, and flies; however, ticks and flies rarely co-occur in the diet of an individual. We observed variability among individuals in their feeding ecology, which is strongly correlated with locality and, to a lesser extent, with the mammal host. We noted a high degree of mobility between hosts within relatively short periods, with 32% of the samples showing traces of at least two mammal hosts. This study illustrates the dynamic foraging behavior of these specialized symbiotic birds, shedding light on their potential role in pest control services and disease transmission.

摘要: The study of parental food provisioning is essential for understanding the breeding ecology of birds. We conducted the first study using accelerometry to detect food provisioning in birds, using Support Vector Machine(SVM) models to identify when adults feed chicks of three different age classes. Accelerometers were attached to the head of adult female Imperial Shags(Leucocarbo atriceps), and various attributes derived from the acceleration signals were used to train SVM models for each chick age class. Model performance improved with chick age class, with SVM models achieving high overall accuracy(>88%) and highest sensitivity in older chick categories(>91%). However, precision values, especially for younger chicks, remained relatively low(between 26% and 45%). The application of a time filter based on the minimum duration of the observed food provisioning behaviours for each chick age category, improved model performance by reducing false provisioning behaviours, particularly in the model for older chicks, which showed the highest precision(72.4%). This study highlights the effectiveness of accelerometry and machine learning in studying parental food provisioning in birds, providing a rapid and accurate data collection method to complement traditional techniques. The described methodology can be applied to any bird species that exhibits distinctive movements while feeding its offspring and has suitable characteristics for attaching an accelerometer to the body part that best captures this movement. Finally, it is hoped that the results of this study will contribute to future research on key questions in parental investment theory and reproductive strategies in birds.

摘要: Common Cuckoos(Cuculus canorus) dependent on parental care for post-hatching demonstrate an intriguing ability to modify their begging vocalizations to ensure maximum care and resources from their interspecific foster parents. Here, we compared begging calls of the Common Cuckoo nestlings fed by four host species, the Grey Bushchat(Saxicola ferreus), Siberian Stonechat(Saxicola maurus), Daurian Redstart(Phoenicurus auroreus),and Oriental Magpie-robin(Copsychus saularis). Results showed that begging calls of the stonechat–, redstart–,and robin–cuckoo resemble those of host species' nestlings in various aspects like low frequency, high frequency,frequency bandwidth and peak frequency, while the bushchat–cuckoo chicks' begging calls were only comparable to their host species in terms of how long they lasted and their peak frequency. In addition, cuckoo nestlings raised in different host nests displayed significant variations in their begging calls in low and peak frequency.This study suggests that cuckoo nestlings do not mimic host species nestlings' begging calls throughout the nestling period, but may tune their begging calls according to host species, while begging calls vary with cuckoo and host species nestlings' ages. Future research should study the parents' reactions to these calls in different host species for a better understanding of the mechanisms underlying such adaptations.

摘要: Many birds develop brood patches on their ventral apterium under hormonal regulation to effectively transmit body heat to eggs during incubation. The developed patch has several characteristics, including de-feathering,vascularization, and edema. However, little is known about whether avian brood parasites that do not incubate their eggs exhibit brood patch development during the breeding season. In this study, we measured the size of the ventral apterium in 114 Common Cuckoos(Cuculus canorus) captured in the field throughout the breeding season and examined the appearance of the ventral apterium to confirm the development of brood patches. We also examined whether morphological traits and various factors correlated with the size of the ventral apterium(sternal apterium and abdominal apterium) and how it changed during the breeding season. We found no clear signs of brood patch development in Common Cuckoos captured throughout the breeding season, indicating that they likely did not develop brood patches on the ventral apterium during this period. We also found that ventral apterium size was positively correlated with wing length and body weight. In addition, Common Cuckoos with newly growing feathers on the boundary of the ventral apterium with pteryla were frequently observed as seasons progressed to the end. In conclusion, Common Cuckoos exhibit neither brood patch development nor the vestigial characteristics of ancestral brood patches, except for the growth of feathers on boundary the ventral apterium. Further studies examining brood patches across different groups of avian brood parasites are valuable for enhancing our understanding of the developmental and physiological adaptations of avian brood parasites.

摘要: The Oriental Reed Warbler(Acrocephalus orientalis) is one of the most commonly used hosts for the parasitic Common Cuckoo(Cuculus canorus). However, as hosts that feed unrelated parasitic nestlings may suffer extra reproductive costs, they may be less willing to care for nestlings that have prolonged nestling periods. To test this hypothesis, the duration of feeding by Oriental Reed Warblers under natural conditions for their own nestlings was compared with the duration of feeding under natural conditions for Common Cuckoo nestlings and for artificially prolonged cuckoo nestlings. The results showed that Oriental Reed Warblers did not starve, drive away, or desert any of the nestlings in the experiment, and neither parent was left alone. Our experimental study indicates that both Oriental Reed Warbler parents were willing to care for nestlings with a prolonged nestling period(up to 30 days, twice the average duration time that the Oriental Reed Warblers fed their own chicks in natural conditions). However, further experiments and observations are required in other host bird species to examine whether both parents or one of the parents may exhibit the behavior of abandoning nestlings with a prolonged nestling period.