Avian Research最新文献

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.

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.

Rivers are important habitats for wintering waterbirds. However, they are easily influenced by natural and human activities. An important approach for waterbirds to adapt to habitats is adjusting the activity time and energy expenditure allocation of diurnal behavior. The compensatory foraging hypothesis predicts that increased energy expenditure leads to longer foraging time, which in turn increases food intake and helps maintain a constant energy balance. However, it is unclear whether human-disturbed habitats result in increased energy expenditure related to safety or foraging. In this study, the scan sample method was used to observe the diurnal behavior of the wintering Spot-billed Duck (Anas poecilorhyncha) in two rivers in the Xin'an River Basin from October 2021 to March 2022. The allocation of time and energy expenditure for activity in both normal and disturbed environments was calculated. The results showed that foraging accounted for the highest percentage of time and energy expenditure. Additionally, foraging decreased in the disturbed environment than that in the normal environment. Resting behavior showed the opposite trend, while other behaviors were similar in both environments. The total diurnal energy expenditure of ducks in the disturbed environment was greater than that in the normal environment, with decreased foraging and resting time percentage and increased behaviors related to immediate safety (swimming and alert) and comfort. These results oppose the compensatory foraging hypothesis in favor of increased security. The optimal diurnal energy expenditure model included river width and water depth, which had a positive relationship; an increase in either of these two factors resulted in an increase in energy expenditure. This study provides a better understanding of energy allocation strategies underlying the superficial time allocation of wintering waterbirds according to environmental conditions. Exploring these changes can help understand the maximum fitness of wintering waterbirds in response to nature and human influences.

The gut microbiota of migratory waterbirds is affected by various complex factors, including cross-species transmission, which increases the risk of pathogen spreading among sympatric animals and poses a potential public health risk to humans. In this study, we investigated the microbial communities of wintering Bean Geese (Anser fabalis), Domestic Ducks (A. platyrhynchos domesticus), humans, and soil using high-throughput sequencing of the 16S rRNA gene region in Shengjin Lake, China. In total, 6,046,677 clean reads were obtained, representing 41,119 operational taxonomic units (OTUs) across the four groups. The dominant microbial phyla were the Proteobacteria, Firmicutes, Bacteroidota, and Actinobacteriota. The Sorensen similarity index and alpha and beta diversity results showed that the gut microbial communities of Bean Geese and Domestic Ducks were more similar to those of the other pairs. Network analysis revealed that Faecalibacterium prausnitzii, Pseudomonas fragi, and Bradyrhizobium elkanii were hubs of the three major modules. Fourteen common microbiomes were identified in Bean Geese, Domestic Ducks, humans, and soil in Shengjin Lake. A total of 96 potential pathogens were identified among the four groups, with 20 specific potentially pathogenic microbiomes found in the gut of Bean Geese. Some of these pathogens are responsible for significant financial losses in the poultry industry and pose risks to human health. Klebsiella pneumoniae, Morganella morganii, Escherichia coli, and Ralstonia insidiosa are potential core pathogens found in the four groups at Shengjin Lake that can cause diseases in humans and animals and facilitate cross-species transmission through various media. Therefore, humans are at risk of contracting these pathogens from migratory birds because of their frequent contact with domestic poultry. However, further studies are required to explore the potential pathogenic species and transmission pathways among sympatric wintering Bean Geese, Domestic Ducks, humans, and soil.

Cold spells and severe weather may have detrimental effects in wild birds, but owing to the stochastic nature of these events, it is not always possible to measure their impacts. In January 2021, a strong snowstorm known as ‘Filomena’ affected Spain, mainly the region of Madrid (Central Spain), which was fully covered with snow and suffered freezing temperatures for a fortnight. Using bird surveys conducted in the winter-spring of 2020 and 2021 (before and after Filomena) at same locations, we addressed the possible impact of the cold spell in three widespread gamebirds: Wood Pigeon (Columba palumbus), Eurasian Magpie (Pica pica) and Red-legged Partridge (Alectoris rufa). No significant abundance differences were found between years for none of the species and hunting pressure was only significantly reduced for Partridges, hence this species may have been negatively affected by Filomena. Results suggest that in response to Filomena, Pigeons conducted partial migration in search of better conditions, while Magpies aggregated in certain areas of Madrid and Partridges endured the harsh conditions within their home ranges. Our results highlight the importance to alleviate negative impacts of extreme weather events in wild birds through management actions, especially for sedentary species.