Avian Research最新文献

Recent advances in our understanding of avian chemical communication have highlighted the importance of olfaction in many aspects of avian life. Prior studies investigating predator avoidance behaviors in response to predator odor cues have produced mixed results across species and contexts. Here we assess if a community of birds in eastern Pennsylvania displays avoidance behaviors towards predator odor cues in a natural foraging setting. We use clay caterpillars to measure foraging activity by birds in the presence of predator (bobcat) urine, non-predator (rabbit) urine, and water controls in two different environmental contexts (field vs. forest). Although we detected a weak trend for birds to forage less at predator urine-treated sites, we found no significant difference in avian foraging between the site types. We did find that foraging rates between environmental contexts changed significantly over the course of the experiment, with forest sites showing decreasing foraging rates and field sites showing increasing foraging rates. Our results reinforce the published literature that avoidance of predator odors by birds may not be ubiquitous across contexts and species.

We examined habitat preferences and nesting requirements of sympatric populations of Middle Spotted Woodpecker (Dendrocoptes medius) and Syrian Woodpecker (Dendrocopos syriacus). We carried out our study in 2015–2018 in natural mountain forests of Southwest Iran. We compared selected features of nesting, territory, and outside territory tree stands of the studied woodpeckers. The Middle Spotted Woodpecker occupied only oak forests, but the Syrian Woodpecker inhabited heterogenic forests that included the preferred tree of this species, the Mount Atlas Mastic. We recorded that in the breeding territories of the Middle Spotted Woodpecker, a greater area covered by tree crowns, as well as a larger number of trees, and a larger trunk basal area were observed in comparison to the territories occupied by the more plastic Syrian Woodpecker. Different habitat preferences demonstrated by both species could be a result of the selection of tree stands that provide the necessary food resources for each woodpecker species. Adaptation of Syrian Woodpecker to use heterogenic forest stands including tree species that produce fruits and as Mount Atlas Mastic trees, which likely allowed this species to colonise in Asia and Europe non-forest tree stands as orchards or gardens. Our results showed that poor tree condition and large tree trunk dimensions had a positive impact on the selection of nesting sites by both species. The presence of trees with large trunk dimensions was associated with multiple years of use of woodpecker breeding sites in the studied forests. Maintaining habitats in suitable condition for both studied woodpeckers can be achieved by preserving natural forests in the mountain regions of Iran.

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.

The House Martin (Delichon urbicum) is a common farmland bird species in the European landscape, yet its population numbers are currently in decline. However, it is not yet sufficiently explained why this long-term decline occurs. To fill this gap in our knowledge, we investigated how land cover composition affects the abundance of House Martins on the landscape scale by using nationwide citizen science data. Utilizing a generalised linear mixed-effect model (GLMM), we evaluated 12,094 records from the Czech Republic spanning 2009–2017. Our analysis underscores the significance of land cover type in shaping House Martin abundance. More specifically, our results indicate that within agricultural land covers “naturally managed arable lands” exhibited significant positive effect, while forests, orchards, and vineyards were deemed less favourable for House Martin populations. Within urban land covers, we found a clear distinction in the impact on House Martin populations, with a positive effect observed in urban infrastructure, development areas, and post-industrial sites (i.e., UrbanAreas), while an indifferent impact was noted within urban green spaces and landscaped areas (i.e., GreenUrban). Notably, our findings suggest that the simple spatial, age, and species structure typical of forests in Europe, and similarly, the uniform structure of parks and gardens, may be responsible for the decline in the abundance of the House Martin. We advocate for the preservation or enhancement of urban greenery, expansion of natural vegetation in rural areas and adoption of ecological management practices in orchards and vineyards to mitigate further declines in House Martin populations.

Despite all efforts, long-term changes in the adult sex ratios of breeding duck populations are still unclear; this uncertainty is especially true for male-bias populations, which are often under the scrutiny of researchers lacking convenient results for the active protection of endangered species. Species with male-bias populations are usually strongly affected by a decline in population size that leads to a higher extinction risk. In this study, we examined our long-term data of the abundance of breeding populations in six duck species (Mallard Anas platyrhynchos, Gadwall Mareca strepera, Red-crested Pochard Netta rufina, Common Pochard Aythya ferina, Tufted Duck Aythya fuligula, and Common Goldeneye Bucephala clangula) from fishponds in South Bohemia, Czechia, between 2004 and 2022. This evidence was used to assess long-term changes in the adult sex ratio in these breeding populations and investigate the possible effects of the NAO index (North Atlantic Oscillation index) on them, indicating climate conditions in winter. We determined a long-term decrease of the proportion of females in the breeding season in two of the six examined species: Common Pochard and Red-crested Pochard, which is driven by the long-term increase in the number of males in contrast to the decreasing or stable number of females likely caused by different migration behaviours between females and males. In the case of Common Pochard, in breeding populations, we estimated 60–65% of males in the early 2000s rising to 75–80% in the early 2020s. However, we establish no significant effects linked to climate conditions of the previous winter in these species as a crucial cause of the changes of the proportion of females in the breeding population.

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.

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.

Although urbanization poses various threats to avifauna, some bird species, including Mallards (Anas platyrhynchos), choose towns and cities as their wintering habitats, possibly due to favourable temperatures and abundant anthropogenic food. In this study, we investigated how population dynamics changed in relation to winter harshness and intensity of supplementary bird feeding in Mallard, a dabbing duck species well adapted to an urban environment. We surveyed 15 city ponds for five consecutive years, counting overwintering individuals and incidents of bird feeding conducted by the citizens of Gdańsk. Number of Mallards observed in the studied area fluctuated both annually and within seasons, with on average 327 (± SD = 108.5) individuals and a male-biased sex ratio reported. We observed a gradient of feeding intensity on the surveyed ponds, with number of feeding incidents ranging from 0 to 30 in a day. The results indicated that the number of Mallards increased with the bird feeding intensity, independently of the size of the studied ponds, and both males and females were similarly attracted by food provisioning. More severe wintering conditions, expressed by the percentage of the ice cover of studied ponds resulted in more birds wintering in the urban area. This effect was more pronounced in females compared to males, possibly due to females having a lower ability to withstand severe wintering conditions, forcing them to relocate towards urban areas. Our results confirm that urbanized areas may serve as wintering grounds for birds, due to additional food resources available there and milder wintering conditions compared to surrounding rural areas.

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.