bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.64898/2026.10.09.757943

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

Cotoara, A. D.·Ledwon, M.·Giuca, R. C.·Todorov, E.·Birau, A.-C.·Osvath, G.
View original source ↗Export metadata ↓

Abstract

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.

Explore related subjects

zoologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Cotoara, A. D., Ledwon, M., Giuca, R. C., Todorov, E., Birau, A.-C., Osvath, G.. 2026-10-12. Rapid interannual reorganisation of Whiskered Tern Chlidonias hybrida breeding colonies within an urban wetland network. https://doi.org/10.64898/2026.10.09.757943

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

What happens when Arctic sea-ice melts? Macroalgae as a summer refuge for sympagic nematode Theristus melnikovi

Sea ice-associated (sympagic) nematodes are particularly vulnerable to ongoing Arctic sea-ice loss, yet the capacity of these sympagic species to persist in ice-free habitats remains poorly understood. We investigated the summer habitat and taxonomic identity of the sympagic nematode Theristus melnikovi, in Svalbard, using an integrative taxonomic approach. We barcoded 17 morphologically identified nematodes from macroalgae (5), sea-ice (9), and sediment (3). Morphological analysis and phylogenetic reconstruction based on 18S rRNA gene analyses revealed that the macroalgae-associated T. melnikovi represented a habitat-associated phenotypic variation of T. melnikovi rather than a morphotype of the benthic nematode T. acer. Macroalgae-associated specimens were generally shorter and stouter, with proportionally longer tails and shorter anterior structures than their ice-associated counterparts, resulting in a superficial resemblance to T. acer. Despite these morphological differences, molecular analyses consistently placed macroalgae-associated individuals within the T. melnikovi clade and haplotype. Our results highlight that T. melnikovi may have a greater ecological flexibility than previously assumed and macroalgae may offer an alternative (summer) habitat, or refuge, during ice-free periods. This capacity could become increasingly important as Arctic sea-ice duration and extent continue to decline.

zoology↗
bioRxiv2026

Repeated coastal observations and molecular confirmation of Alatina grandis (Cubozoa: Alatinidae) in the Gulf of Aqaba, Red Sea

Cubozoans are rarely documented in the Red Sea, and the taxonomic identity of large alatinid medusae previously reported from the Gulf of Aqaba has remained uncertain. Historical observations from Eilat in 1997 and 2000 were reported as Carybdea alata, although their exceptionally large size was recognized as being within the range of C. grandis (currently Alatina grandis); unresolved carybdeid taxonomy at the time prevented a definitive species-level assignment. Following more than two decades without documented observations, five large alatinid medusae were recorded on separate occasions along the Eilat coastline between July 2025 and August 2026. One specimen was collected, while high-resolution in situ photographs and video recordings of live medusae provided material for morphological assessment. Diagnostic morphological characters were consistent with Alatina grandis, and molecular analysis of the collected specimen independently confirmed its identity as A. grandis. These findings provide the first molecular confirmation of A. grandis from the Gulf of Aqaba and the Red Sea and establish the identity of the alatinid medusae documented during the recent series of observations. The clustering of five observations within one year, following more than two decades without documented occurrences, raises questions regarding the temporal occurrence and distribution of this rarely reported cubozoan in the northern Red Sea.

zoology↗
bioRxiv2026

Shifts in the Maternal Gut Microbiome Across Pregnancy are Associated with Energetic Status in Phayre's Leaf Monkeys

During pregnancy, mothers experience physiological changes that support fetal development, including shifts in energy utilization and increasing insulin resistance during late gestation. While these changes benefit the fetus, they can also impose energetic costs that affect the mother's physical condition and metabolic phenotype. Previous studies suggest that the gut microbiome, a key regulator of female metabolism and energy harvest, may play a critical role in mediating these physiological challenges. In this study, metagenomic sequencing of the gut microbiome of 120 samples revealed dramatic shifts in gut bacterial composition and function associated with pregnancy and lactation in 14 wild Phayre's leaf monkeys, Trachypithecus phayrei crepusculus, from two groups at the Phu Khieo Wildlife Sanctuary, Thailand. Alpha diversity, beta diversity, and taxonomic composition all differed between cycling and the 3rd trimester. Furthermore, bacterial dissimilarity between these states was negatively correlated with postpartum physical condition; that is, mothers whose gut microbiota remained more stable during pregnancy recovered sooner after giving birth. Functional profiling revealed a depletion of pathways involved in purine salvage and glutamate degradation during the 3rd trimester. Overall, our study demonstrates that the gut microbiome undergoes substantial changes during pregnancy, and the stability of these microbial communities predicts postpartum maternal health and potentially influence lifetime reproductive output.

zoology↗