Biology subjects

Osvath, G.

Publications and source records attributed to Osvath, G..

5 recordsLinked to original sources

bioRxiv2026

Rapid interannual reorganisation of Whiskered Tern Chlidonias hybrida breeding colonies within an urban wetland network

Colonial waterbirds breeding in unstable wetland habitats are expected to show flexible colony-site use, but how breeding activity redistributes within small networks of alternative nesting sites, particularly in urban wetlands, is poorly documented. We quantified the spatial organisation of breeding Whiskered Terns Chlidonias hybrida across nine lakes of Vacaresti Natural Park, a spontaneously developed urban wetland in Bucharest, Romania, using nest counts repeated every one to three weeks over four breeding seasons (2022-2025). The number of occupied lakes fell from nine in 2022 to three in 2024, before a partial recovery to six in 2025, while the annual peak of simultaneously active nests ranged from 53 (2024) to 222 (2025). Spatial concentration at the annual peak survey was higher in 2024-2025 (dominant-lake proportion 0.55-0.56; Simpson's concentration index C = 0.42-0.50) than in 2022-2023 (0.41-0.46; C = 0.29-0.32), and the peak-survey distributions of 2024 and 2025 showed no overlap (Bray-Curtis dissimilarity = 1.0). The breeding season was long and asynchronous in 2022, when the largest colony shifted repeatedly among lakes, but compressed and synchronised in 2024-2025, when a single lake remained dominant throughout the season. Lake surface area (0.18-2.25 ha) was not detectably associated with occupancy or seasonal maximum nest numbers. These results indicate highly flexible colony-site use and rapid interannual reorganisation of breeding activity within a compact network of alternative nesting sites. Conservation and monitoring of urban wetland colonies should therefore encompass the entire network of potential nesting sites rather than only the currently dominant colony site.

zoology↗

bioRxiv2026

Mapping feather vane structure across the avian wing: spatial variation, asymmetry, and the effect of flight style

Flight feather vanes are the primary aerodynamic surface of the avian wing. Because loading varies across the wing, vane macrostructure should co-vary with local mechanical demands, yet comparative data on how barb and barbule traits change among remiges and between vane surfaces remain scarce. We quantified barb density, barbule density, barb angle, barb length, and vane width on both vanes at three measurement positions along the rachis of all remiges in four species with contrasting flight modes (white stork, common buzzard, house sparrow, pygmy cormorant), generating over 40,000 measurements across 15 response variables from 992 feathers of 41 individuals. Two complementary generalised additive models characterised variation along the spanwise, inter-vane, and longitudinal axes, and compared outer primaries, inner primaries, and secondaries as functional wing regions. Feather macrostructure varied along all three axes and outer primaries represent the most distinctive region, with lower leading-vane barb density, reduced barb angles, and vane width asymmetry two to three times higher than in inner primaries or secondaries. House sparrow exhibited the densest vane architecture and the highest vane width asymmetry, whereas the low wing-beat frequency species showed complex nonlinear spanwise patterns undetectable by single-feather sampling. Pygmy cormorant barbule density was 39-53% lower than in all other species, matching its wettable plumage strategy. Longitudinal gradients in barb density and barb angle (22-31% decline) were conserved across species. The avian wing is thus functionally regionalised at the macrostructural level, with vane architecture reflecting both aerodynamic and ecological pressures. Summary statementFine-scale vane measurements across all remiges in four species show macrostructural regionalisation of the avian wing, with outer primaries showing the most distinctive vane architecture.

zoology↗

bioRxiv2026

The lost vultures of Romania: reconstructing two centuries of decline from historical records (Gyps fulvus, Aegypius monachus, Neophron percnopterus, Gypaetus barbatus)

Romania represents one of the few European Union member states in which all four Old World vulture species historically maintained breeding populations: the Griffon Vulture (Gyps fulvus), Cinereous Vulture (Aegypius monachus), Egyptian Vulture (Neophron percnopterus) and Bearded Vulture (Gypaetus barbatus). Until ongoing reintroduction efforts, Romania remained among the last EU countries whose former vulture guild had not yet been targeted for active recovery. Despite this exceptional significance in a European conservation context, no comprehensive synthesis of the historical and contemporary distribution of these species in Romania has been undertaken. We conducted an extensive review to gather all available vulture occurrence data and present a database of 1,136 occurrence records spanning 1818-2025. We systematically searched museum collections, historical ornithological literature, modern field surveys and citizen-science platforms. The database documents substantial breeding populations across the Carpathian arc and Dobrogea until the early twentieth century, followed by near-total breeding collapse between the 1920s and 1960s driven by persecution, secondary poisoning and agrarian transformation. In total, 148 confirmed or probable breeding records have been documented for the four species combined, with the most recent confirmed breeding records dating to 1929 (Gyps fulvus and Gypaetus barbatus), 1942 (Aegypius monachus) and 1966 (Neophron percnopterus). Non-breeding occurrences increase markedly after 2010, consistent with dispersal from expanding Balkan source populations. The F[a]g[a]ras and Retezat Mountains emerge as the historically most important breeding strongholds for three of the four species (all except the Egyptian Vulture). This dataset highlights the value of reconstructing historical baselines where functional extinction preceded modern monitoring, and provides an empirical foundation for reassembling a keystone scavenger guild in the Carpathian-Danube region.

zoology↗

bioRxiv2023

Geographic distribution of feather δ34S in Europe

Geographic distribution models of environmental stable isotopes (so called isoscapes) are widely employed in animal ecology, wildlife forensics and conservation. However, the application of isoscapes is limited to elements and regions for which the spatial patterns have been estimated. Here, we focused on the ubiquitous yet less commonly used stable sulfur isotopes ({delta}34S). To predict the European{delta} 34S isoscape, we used 242 feather samples from Eurasian Reed Warbler (Acrocephalus scirpaceus) formed at 69 European wetland sites. We quantified the relationships between sample{delta} 34S and environmental covariates using a random forest regression model and applied the model to predict the geographic distribution of{delta} 34S. We also quantified within-site variation in{delta} 34S and complementarity with other isotopes on both individual and isoscape levels. The predicted feather{delta} 34S isoscape shows only slight differences between the central and southern parts of Europe while the coastal regions were most enriched in 34S. The most important covariates of{delta} 34S were distance to coastline, surface elevation and atmospheric concentrations of SO2 gases. The absence of a systematic spatial pattern impedes the application of the{delta} 34S isoscape but high complementarity with other isoscapes advocates the combination of multiple isoscapes to increase precision of animal tracing. Feather{delta} 34S compositions showed considerable within-site variation with highest values in inland parts of Europe, likely attributed to wetland anaerobic conditions and redox sensitivity of sulfur. The complex European geography and topography as well as using{delta} 34S samples from wetlands may contribute to the absence of a systematic spatial gradient of{delta} 34S values in Europe. We thus encourage future studies to focus on the geographic distribution of{delta} 34S using tissues from diverse taxa collected in various habitats over large land masses in the world (i.e., Africa, South America or East Asia). Open Research statementSample metadata are stored and available for reuse in the AviSample Network database (https://avisample.net/: AS00001-AS00117; Brlik et al. 2022b). The information on the isotopic composition and geographic origin of feather samples used to produce the{delta} 34S isoscape, predicted feather{delta} 34S,{delta} 2H and{delta} 13C isoscapes are publicly available from the Zenodo data repository at https://doi.org/10.5281/zenodo.7315567 (Brlik et al. 2022c).

ecology↗

bioRxiv2020

Varietas delectat: groups with diverse personalities mitigate physiological stress in a songbird

Social groups often consist of diverse phenotypes, including personality types, and this diversity is known to affect the functioning of the group as a whole. Social selection theory proposes that group composition (i.e. social environment) also influences the performance of individual group members. However, the effect of group behavioural composition on group members remains largely unexplored, and it is still contentious whether individuals benefit more in a social environment with homogeneous or diverse behavioural composition. We experimentally formed groups of house sparrows Passer domesticus with high and low diversity of personality (exploratory behaviour), and found that their physiological state (body condition, physiological stress and oxidative damage) improved with increasing group-level diversity of personality. These findings demonstrate that group personality composition affects the condition of group members and individuals benefit from social heterosis (i.e. associating with a diverse set of behavioural types). This aspect of the social life can play a key role in affiliation rules of social animals and might explain the evolutionary coexistence of different personalities in nature.

ecology↗