Avian Research最新文献

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.

Weather conditions play a pivotal role in embryo development and parental incubation costs, potentially impacting the clutch size and incubation behavior of birds. Understanding these effects is crucial for bird conservation. Reeves's Pheasant (Syrmaticus reevesii) is a threatened species endemic to China, which is characterized by female-only incubation. However, there is a lack of information regarding the impact of weather conditions on clutch size and incubation behavior in this species. Using satellite tracking, we tracked 27 wild female Reeves's Pheasants from 2020 to 2023 in Hubei Province, China. We explored their clutch size and incubation behavior, as well as their responses to ambient temperature and precipitation. Clutch size averaged 7.75 ± 1.36, had an association with average ambient temperature and average daily precipitation during the egg-laying period, and was potentially linked to female breeding attempts. Throughout the incubation period, females took an average of 0.73 ± 0.46 recesses every 24 h, with an average recess duration of 100.80 ± 73.37 min and an average nest attendance of 92.98 ± 5.27%. They showed a unimodal recess pattern in which nest departures peaked primarily between 13:00 and 16:00. Furthermore, females rarely left nests when daily precipitation was high. Recess duration and nest attendance were influenced by the interaction between daily mean ambient temperature and daily precipitation, as well as day of incubation. Additionally, there was a positive correlation between clutch size and recess duration. These results contribute valuable insights into the life-history features of this endangered species.

Avian interspecific brood parasitism is an excellent system for studying coevolutionary processes in nature because brood parasites directly affect host reproductive success. Most research on avian brood parasitism has, therefore, focused primarily on specific host anti-parasite behaviours and parasite counter-adaptations. However, the population-level consequences of brood parasitism for host species are poorly understood. This study investigated the effect of Common Cuckoo (Cuculus canorus) parasitism on the productivity of a local population of the Great Reed Warbler (Acrocephalus arundinaceus) host in south-western Slovakia. A total of 495 females nesting at the studied site successfully fledged 1321 of their own young and 63 young of the Common Cuckoo over the course of 15 years (2008–2022), and the annual rate of successful parasitism ranged from 18% to 44% over this period. As predicted, higher rates of successful cuckoo parasitism significantly reduced the annual productivity of the local Great Reed Warbler population, and its contribution to decreased host reproductive success was at about the same rate as overall nest failure caused by predation and other environmental factors. Such a heavily parasitized population was probably maintained by immigrants from other populations and density-dependent selection, which is also consistent with source–sink dynamics. However, further long-term studies monitoring parasitized populations are required to confirm these findings.

Soaring bird migration often relies on suitable terrain and airflow; therefore, route selection is vital for successful migration. While age and experience have been identified as key factor influencing migration route selection among soaring raptors in the African-Eurasian Flyway, how they shape the migration route of soaring raptors in East Asia is still largely unknown. In this study, we investigated potential variations in the routes and timing in autumn migration of juvenile and older soaring birds, using count data of Greater Spotted Eagles (Clanga clanga) from two coastal sites and two inland sites in China. From 2020 to 2023, we recorded a total of 340 individuals, with the highest site averaging over 90 individuals per autumn, making it one of the world’s top single-season counts and thus a globally important site for this species. We found that 82% and 61% records from coastal sites were juveniles, significantly higher than inland sites (15% and 24%). Juveniles at all four sites exhibited markedly earlier median passage time than non-juveniles, with brief overlapping in their main migration periods. Both coastal sites are located on the tip of peninsulas stretching southwest, requiring long overwater flights if crossing the Bohai Bay or Beibu Gulf, which would be energetically demanding and increase mortality risk. Experienced individuals may have learned to avoid such terrain and subsequent detour, while juveniles are more prone to enter these peninsulas due to lack of experience and opportunities for social learning, or following other raptor species that are more capable of powered flight. Our findings highlight the importance of age and experience in migration route selection of large soaring birds.

Since the time of Darwin, subspecies have been recognized as an initial stage in the evolution of species. However, the impact of dispersal on subspecies richness in birds globally has received little attention, despite dispersal being a key factor in determining the rate of evolution and playing a significant role in evolutionary divergence. Therefore, it is important to conduct a comprehensive study to address this issue. In this study, we aimed to assess the association between subspecies richness (measured by the number of subspecies) and dispersal ability (measured by the hand-wing index) on a global scale, using a dataset of over 7000 bird species. Our results revealed a negative correlation between dispersal ability and the number of subspecies, without any quadratic correlation. The wing is a crucial phenotypic trait for birds, and the concept of subspecies is important in speciation theory and conservation biology. Therefore, our findings not only enhance our understanding of the association between avian morphological traits and evolutionary divergence but also have implications for the conservation of avian species diversity.

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.

Shorebird populations are declining worldwide, mainly due to human disturbances and loss of coastal wetlands. However, supratidal habitats as saltpans could play a role in buffering human impact. Saltpans have shown to be important as feeding or breeding sites of some shorebird species. A potential conservation strategy to increase shorebird populations in saltpans is to manipulate the cues that birds use to select optimal breeding habitat. Here it is hypothesized that shorebirds are attracted to bivalve shells due to the advantages they offer. Following this hypothesis, we supplemented a restored saltpan in 2019 and 2021 with bivalve shells, expecting an increase in the number of breeding birds’ nests. More than 75% of Kentish Plover (Charadrius alexandrinus) and Little Tern (Sternula albifrons) nests were found in patches with shells in both years. The best model for both species indicates that the presence of shells is the factor that most correlates with the location of nests. The probability of choosing one place over another to settle their nest increases in areas with an abundance of shells, double in the case of the Kentish Plover and triple in the case of the Little Tern. The result of this study may constitute a valuable tool for attracting birds to restored saltpans and could contribute to the success of expensive restoration projects where time is usually a constraint.

Due to a complex geological and biotic history, the Isthmus of Tehuantepec (IT), has been long recognized as a driver for the evolutionary divergence of numerous lowland and highland taxa. Widely distributed in the lowlands of the American continent, the White-Tipped Dove (Leptotila verreauxi) is a polytypic species with 13 recognized subspecies. Four of these have been recorded in Mexico, and the distribution of three abuts at the IT, suggesting a contact zone. To estimate phylogenetic patterns, divergence times and genetic differentiation, we examined two mtDNA (ND2 and COI) and one nDNA (β-fibint 7) markers. We also used correlative ecological niche models (ENM) to assess whether ecological differences across the IT may have acted as a biogeographical boundary. We estimated paleodistributions during the Middle Holocene, Last Glacial Maximum and Last Interglacial, to evaluate the influence of climate changes on the distribution and demographic changes. Our results showed genetically distinct lineages that diverged approximately 2.5 million years ago. Climatic and ecological factors may have played a dual role in promoting differentiation, but also in the formation of a secondary contact zone in the southern IT. Our ecological niche comparisons indicated that the ecological niche of sympatric lineages at the IT are not identical, suggesting niches divergence; in addition, environmental niche models across the region indicated no abrupt biogeographic barriers, but the presence of regions with low suitability. These results suggest that genetic differentiation originated by a vicariant event probably related to environmental factors, favored the evolution of different ecological niches. Also, the absence of a biogeographic barrier but the presence of less suitable areas in the contact regions, suggest that secondary contact zones may be also maintained by climatic factors for the eastern group, but also by biotic interactions for the western group.