Avian Research最新文献

Animals must strike a balance between anti-predation behavior and other essential behaviors, such as foraging. Within the same species, strategies may vary on individuals' risk-taking preferences, and in this process the environment is a determinant, in addition to predator regime. The Crested Ibis (Nipponia nippon) exhibits such tendency. This is an endangered species, once inhabiting exclusively in China's Qinling Mountain. This used to be the sole remaining wild population. However, over recent decades, this population has expanded. A portion has relocated to breed in the lower plain area, which is characterized by elevated level of human activities and landscape complexity. We used flight initiation distance (FID) as an indicator of the ibises' risk-taking preference, particularly their response to human proximity. Additionally, we examined the environmental factors influencing their foraging site selection, including altitude, terrain openness, human activity intensity and human construction. Our findings revealed a significantly shorter FID among individuals relocating to plain habitats, indicating a higher tolerance of human proximity. The results showed that FID decreased with distance to the nearest human settlement. Another finding is that FID was independent of instant human activity intensity and environmental factors (altitude and terrain openness). These different may arise from various combinations of human activity, predation risk, and food abundance within the two habitats. These results provide insights into the in situ conservation of the threatened species within the context of global urbanization.

Sex-biased mortality can occur in birds during development, for example due to sexual differences in energy requirement and/or environmental sensitivity, or the effects of sex hormones or sex differences in the expression of mutations linked to sex chromosomes. The extent of sex-bias in mortality may also be related to environmental conditions that influence offspring development and survival. Urban areas often provide poorer conditions for nestling development resulting in higher offspring mortality compared to natural areas, which may accelerate sex differences in offspring mortality in cities. To test this hypothesis, we examined the sex ratio of dead offspring in Great Tits (Parus major), using 427 samples of unhatched eggs and dead nestlings collected in two urban and two forest sites between 2013 and 2019. The ratio of males in the whole sample of dead offspring (56.9%) was significantly higher than expected by an 1:1 ratio, and the strongest sex biases were detected in urban areas (57.6% males) and in young nestlings (<14 days old, 59.0% males). However, the sex ratios of dead offspring did not differ significantly among study sites and between offspring developmental stages. 29.3% of unhatched eggs contained a visible embryo, and the proportion of embryo-containing unhatched eggs did not differ significantly between urban and forest study sites. These results suggest male-biased offspring mortality in Great Tits, and highlight the need of large datasets to detect subtle differences between habitats and developmental stages.

Population genomic data could provide valuable information for conservation efforts; however, limited studies have been conducted to investigate the genetic status of threatened pheasants. Reeves's Pheasant (Syrmaticus reevesii) is facing population decline, attributed to increases in habitat loss. There is a knowledge gap in understanding the genomic status and genetic basis underlying the local adaptation of this threatened bird. Here, we used population genomic data to assess population structure, genetic diversity, inbreeding patterns, and genetic divergence. Furthermore, we identified candidate genes linked with adaptation across the current distribution of Reeves's Pheasant. The present study assembled the first de novo genome sequence of Reeves's Pheasant and annotated 19,458 genes. We also sequenced 30 individuals from three populations (Dabie Mountain, Shennongjia, Qinling Mountain) and found that there was clear population structure among those populations. By comparing with other threatened species, we found that Reeves's Pheasants have low genetic diversity. Runs of homozygosity suggest that the Shennongjia population has experienced serious inbreeding. The demographic history results indicated that three populations experienced several declines during the glacial period. Local adaptative analysis among the populations identified 241 candidate genes under directional selection. They are involved in a large variety of processes, including the immune response and pigmentation. Our results suggest that the three populations should be considered as three different conservation units. The current study provides genetic evidence for conserving the threatened Reeves's Pheasant and provides genomic resources for global biodiversity management.

Endosymbiotic bacteria of insects can facilitate host expansion into novel niches by providing their host with a fitness benefit such as vitamins or amino acids that are otherwise lacking in their hosts' diet. This close association can lead to cospeciation between insects and their symbionts; however, the symbionts’ small genome size leaves it susceptible to genome derogation which can result in symbiont replacement. Here, we screen chewing lice infesting shorebirds and terns to see what endosymbiotic bacteria are present, and build a summary phylogeny that includes louse endosymbiont sequences from this study as well as those from other louse genera, insects and bacteria strains from GenBank. We found a Sodalis-allied endosymbiont in Carduiceps, Lunaceps, Quadraceps, and Saemundssonia, as well as symbionts belonging to the family Enterobacteriaceae in Lunaceps, and Quadraceps. No louse species were host to both endosymbionts; however, the birds Kentish Plover (Charadrius alexandrinus) and Greater Crested Tern (Thalasseus bergii) were host to two genera of lice, each of which was infested with a different group of endosymbionts. In the summary phylogeny the endosymbionts from shorebirds, and tern lice did not form a monophyletic group, and therefore likely acquired their bacterial endosymbionts multiple times.

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 semi-continuously 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.

With continually increasing urbanization, the land cover in urban areas continues to change, resulting in the loss of biodiversity. Birds are highly sensitive to changes in habitat. Most forest birds perch on plants that provide increased safety to reduce the risk of predation, and small birds may also consider insulation when using roosting plants in winter because of cold weather. Landscaping plants thus shape the nocturnal roosting environment of urban birds, and proper planting is essential for the survival of birds at night. The use of roosting plants by urban birds should therefore be studied to provide a reference for landscaping. In the current study, we observed 1865 nocturnal roosting birds in Beijing from 2021 to 2022, with 23 species of birds from 12 families and 45 species of plants from 22 families recorded. Juniperus chinensis exhibited the highest bird rarity-weighted richness, followed by Fraxinus pennsylvanica, Phyllostachys propinqua, Pinus tabuliformis, and Ulmus pumila. The diameter at breast height, tree height, and crown width of plants used by birds was largest in summer and smallest in winter, and the perch height of birds was the highest in spring and summer and the lowest in winter. Birds used the highest proportion of deciduous plants in summer and the highest proportion of evergreen plants in winter. A significant seasonal difference in the use of evergreen and deciduous plants by small birds was noted, with a preference for deciduous plants in summer and evergreen plants in winter, while this preference was not found in large birds. These findings indicate that evergreen plants provide a vital nocturnal roosting environment for small birds in winter. To provide a better nocturnal roosting habitat for urban birds, we recommend paying attention to the combination of evergreen and deciduous plants when carrying out landscape construction.

Identifying factors affecting the survival of individuals is essential for understanding the evolution of life-history traits and population dynamics. Despite numerous studies on this subject in north-temperate environments, there is a lack of equivalent studies at similar latitudes in the south. Here, we used a 14-year dataset of capture, banding, and resighting to estimate the annual variation in the apparent adult survival probability of a south-temperate population of House Wrens (Troglodytes aedon bonariae). We evaluated temporal variation in survival and the effect of environmental (climatic) and demographic variables (adult abundance, total number of fledglings produced during each breeding season) on survival estimators. We found that the probability of adult survival decreased as the abundance of breeding adults increased. This density-dependent effect could be related to the resident lifestyle of southern House Wrens, which could determine an intense competition for territories and resources that ultimately would affect their survival.

Biological specimens are fundamental for taxonomy and flora/fauna research. More importantly, they also play crucial roles in recording environmental impacts on morphology and behavior, which is vital for biodiversity research and conservation. However, there are few systematic studies on the patterns and drivers of bird specimen number at regional scales. This study is the first attempt to examine the relationships between bird specimen number and species traits as well as climate niche breadth in China, aiming to answer two questions: 1) how do species’ temperature niche breadth and precipitation niche breadth influence specimen number? 2) which trait is most associated with bird specimen number? The associations between bird specimen number and explanatory variables were examined using ordinary least squares, generalized linear models, phylogenetic generalized linear mixed models, and multiple comparisons. The results showed that Muscicapidae was the family with the highest specimen number, and Passeriformes was the order with the highest specimen number. Bird specimen number significantly increased with larger temperature niche breadth and precipitation niche breadth. Specimen number was also positively associated with geographic range size, habitat specificity, hunting vulnerability and clutch size, but negatively associated with body size. These findings suggest that future bird specimen collection should pay more attention to birds with limited ecological niches, large body sizes, and small clutch sizes. This research enhances the use of bird specimen data to study and preserve biodiversity.