Search bioRxiv⌕ 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

A comprehensive identification protocol for postcranial bones of Southeast Asian Ruminantia. Part 2: Morphological criteria for small and medium-sized species

The taxonomic identification of postcranial elements from small and medium-sized ruminants represents a significant challenge in zooarchaeological and Late Quaternary paleontological studies, particularly in biodiversity-rich regions such as continental Southeast Asia. This study presents a comprehensive osteological reference framework for the small and medium-sized Ruminantia of this region, based on a comparative sample of 228 specimens representing 14 species across three families (Bovidae, Cervidae, and Moschidae). Osteological characters were first described on a small initial specimen set and subsequently scored across the full sample. Although a small number of character states were found to be unique to specific taxa, most proved highly variable, limiting their individual identification potential. To address this, a Random Forest and a Naive Bayes classifier were applied to assess the discriminatory power of character combinations across four taxonomic ranks (Family, Subfamily, Genus, and Species) on independent bones. Both approaches performed similarly, achieving mean identification accuracies of 87-86% at the family level, 69% at the subfamily level, 50% at the genus level, and 35-33% at the species level. The Naive Bayes models were further deployed as an interactive web application, allowing users to perform bone identification based on any combination of observable character states from a single anatomical element. Our results highlight the limits of morphological identification of postcranial elements in this taxonomic and biogeographic context, while demonstrating that a transparent, reproducible, and statistically grounded approach can still represent a significant step forward for zooarchaeological and Late Quaternary paleontological studies in Southeast Asia and beyond.

zoology↗
bioRxiv2026

A comprehensive identification protocol for postcranial bones of Southeast Asian Ruminantia. Part 3: Morphological criteria for large-sized species

Postcranial remains of large-bodied ruminants are abundant in the Late Quaternary record of continental Southeast Asia, yet their taxonomic attribution remains one of the least resolved problems in the zooarchaeology of this biodiversity-rich region. We address it here with an osteological identification protocol covering the six large ruminant species of the mainland: Bubalus bubalis, Bos javanicus, Bos sauveli, Bos gaurus, Budorcas taxicolor and Rusa unicolor, built from a comparative sample of 109 skeletons. A total of 148 discrete characters over 27 skeletal elements representing 442 states were defined on a restricted set of individuals, then scored across the entire sample. Most proved remarkably stable within taxa with 80.0% of the character/taxon combinations showing a dominant state at a frequency above 95%, and a substantial number of states occurred in a single family, subfamily, genus or species. Character combinations for taxonomic identification were then evaluated by the use of two supervised machine learning methods, a random forest model and a naive Bayes classifier at each of four taxonomic ranks. The two behaved almost identically, with mean accuracies of 95-94% for families, 93% for subfamilies, 89% for genera and 76% for species; only the three closely related and unevenly sampled species of Bos resisted consistent separation. The weighted naive Bayes models are distributed as a standalone web application in which any combination of states observed on a single element returns attribution probabilities for every rank. Together these results offer a transparent and statistically explicit alternative to expert judgement for the identification of Late Quaternary postcranial mammal remains, in Southeast Asia and elsewhere.

zoology↗
bioRxiv2026

Note on a Small Chlamyphoridae (Xenarthra, Cingulata) from the Amazon, Brazil

The Awa-Guaja are one of the last hunter-gatherer peoples in the world and live in Indigenous reserves in northwestern Maranhao, Brazil. The Guaja Ethnographic Collection consists of animal remains found during excavations of the community s refuse areas, conducted between 1987 and 1990. This study presents a taxonomic reassessment of a small Cingulata specimen from this collection. The specimen, previously identified as Euphractus sexcinctus, consists of a complete right femur whose taxonomic identity was reevaluated through comparative morphological and metric analyses using specimens from scientific collections and data from the specialized literature. The results revealed that the femur is smaller than those observed in individuals of E. sexcinctus and exhibits a combination of anatomical features resembling those found in the genera Chaetophractus, Cabassous, and Euphractus. Despite these similarities, the observed morphological differences do not allow a reliable identification at the genus level. Therefore, the specimen was provisionally assigned to the family Chlamyphoridae, and its identification was retained at the family level.

zoology↗