Ex-situ breeding programs often utilize pedigree-analysis to select breeding pairs with the goal of maximizing retention of genetic variation and establishing self-sustaining populations. These efforts are limited when selected pairs fail to reproduce successfully. Because mate-choice serves an important role in many mating systems, providing the opportunity to engage in this behavior could lead to greater pair compatibility and offspring survival. In this study, we investigated the impact of female mate-choice on reproductive success and animal welfare of two passerine species: blue-gray tanagers (Thraupis episcopus) and red-capped cardinals (Paroaria gularis). One group of females were allowed to demonstrate a preference between three potential males and were subsequently paired with their preferred mate. A second group of females were paired with their pedigree-assigned partner. We measured a variety of reproductive parameters (onset of nesting, number of eggs, and number of fledglings) and evaluated animal welfare using positive (behavioral diversity) and negative (fecal glucocorticoid metabolite) indicators of welfare. There was no statistically significant difference in reproductive success based on pairing method for either species. Females allowed to choose their mate had significantly higher behavioral diversity than those assigned a mate (p < 0.03), however there was no difference in male behavioral diversity between the two groups. These findings suggest that the opportunity for mate-choice may lead to greater welfare, but only for the individual expressing preference. Outcomes of the study highlight the many variables that can affect reproductive success and the considerable research still needed.

Recent years have seen an explosion in examples of supergenes, where recombination is suppressed between haplotypes, often via inversion polymorphisms, to control complex traits. However, an enduring problem in evolutionary biology is understanding the molecular consequences of recombination suppression, especially when it has been present for long periods. Here, we explore the molecular evolution of the A and B haplotypes of a large, sex-linked inversion polymorphism in a passerine bird, the zebra finch (Taeniopygia guttata, ) responsible for most of the genetic variation in sperm morphology. We find evidence for reduced efficacy of purifying selection acting on the coding sequence of the Z-linked haplotypes and an increase in mutational load. However, we fail to find a positive association between expression and sequence divergence, consistent with an absence of any compensatory expression evolution for the accumulation of deleterious alleles.

Coexistence between migratory birds and wind energy production: The Gotthard wind park (Switzerland) as a case study.

Coping with extremes: diet and phylogeny shape gut microbiota in six passerine species inhabiting the Qinghai-Tibet Plateau

West Nile Virus (WNV) is a zoonotic arbovirus maintained in a transmission cycle between Culex mosquitoes and birds, occasionally spilling over into humans. The impact of avian biodiversity on WNV circulation remains debated, with studies reporting both negative and positive correlations (dilution and amplification effects respectively) across different settings. In Europe, this relationship remains largely unexplored, particularly in regions with high WNV transmission, such as Emilia-Romagna in Northern Italy. We explored the association between avian biodiversity and WNV circulation in Culex mosquitoes in Emilia-Romagna using 11 years (2013-2023) of entomological surveillance data paired with two avian data sources. We calculated avian biodiversity indices (Shannon's, Simpson's, and Chao2) from observation records from the Farmland Bird Index project and applied linear regression models to assess their relationship with WNV detection frequency. Moreover, we used Bayesian spatiotemporal regression models and gridded weekly avian abundance estimates from the eBird project to analyse the associations between avian species richness indices and WNV transmission risk quantified by vector index (VI) at 68 geolocated mosquito traps across the region. We observed consistent negative associations between WNV detection frequency in the Culex population and avian biodiversity indices, supporting the dilution effect hypothesis (DEH). We found that non-passerine species richness was negatively associated with VI while passerine species richness showed a positive association after adjusting for covariates and spatial random effects. These findings suggest that passerines may amplify WNV transmission, whereas the presence of non-passerine species is associated with reductions in WNV circulation. This study provides the first empirical evidence supporting the DEH for WNV in Europe. These findings have important implications for biodiversity conservation and integrated public health surveillance activities across Europe.

Agricultural intensification, particularly shifts from traditional rainfed to irrigated crops, profoundly alters habitats and biodiversity. In this work, we examined the effect of such transformations on a wintering passerine assemblage in a Mediterranean agro-forestry mosaic in Spain. Sampling was conducted in a reed bed area used as a roosting site for several passerine species that depend on surrounding cropland to feed, during winters 2004/05-2006/07 (pre-irrigation) and 2021/22-2023/24 (post-irrigation). Findings reveal a significant reduction in species richness (from 24 to 12 species) as confirmed by rarefaction analyses. Assemblage composition shifted markedly, with specialist seed-eaters declining, whilst wetland-adapted species increased. Such result aligns with the expected ecological impact of irrigation, which simplifies habitats and favors generalist species, underscoring the biodiversity impact of irrigation policies. Such transformation contributes to deteriorating Spain’s role as a critical wintering ground for several European species. Our findings appeal to an urgent need for adaptive management policies to mitigate biodiversity loss in Mediterranean agro-ecosystems under agricultural intensification. Future research should explore broader regional impacts and the interplay of climate change with irrigation-driven biodiversity shifts.

Factors shaping three-dimensional territories of song birds in northern boreal habitats: the first results

In June 2024, a genomic cluster of seven Salmonella Typhimurium - sequence type 19, and cluster type 21092 - was detected in Norway, triggering a national outbreak investigation. Information about new cases was collected from the Norwegian Surveillance System for Communicable Diseases and the database at the National Reference Laboratory for Enteropathogenic Bacteria (NRL) at the Norwegian Institute of Public Health (NIPH). Microbiological analyses were conducted by NRL at NIPH for human samples and at the Norwegian Veterinary Institute for animal samples. Epidemiological data was collected through interviews. International notification was sent via EpiPulse. Eleven cases in total, sampled between March 6 and July 11, 2024, were identified across Norway. The median age of affected individuals was three years. Notably, 73% of the cases reported prior contact with cats or passerine birds. The outbreak strain was also detected in a faecal sample from a cat belonging to one of the affected households, suggesting an animal source. Concurrently, Finland and Sweden reported five and six cases, respectively, involving the same outbreak strain. Several of these individuals also reported contact with cats or birds. Passerine birds are a well-documented reservoir for S. Typhimurium in the Nordic region, often leading to transmission to both cats and humans. This outbreak highlights the role of animal exposure in the spread of S. Typhimurium and emphasize the need for timely, targeted public health communication on infection prevention measures.

Torpor is a controlled physiological state of reduced metabolism and typically body temperature (Tb) used by some endothermic animals to reduce their resting energy expenditure1,2 and increase survival during unfavorable environmental conditions.3,4,5,6 Passerine birds, the largest avian order, have long been considered limited to shallow reductions of Tb (min. Tb usually >30°C; undocumented <23°C) during part of their rest phase,7,8 with deeper and longer torpor restricted to a few non-passerine bird groups.9 Here, we used temperature telemetry to record the skin temperature (Ts; as a close proxy for core Tb) of free-living white-backed swallows (Cheramoeca leucosterna; 15 g) during winter in inland Australia. This species is an aerial foraging passerine bird that roosts in burrows. On most nights, we measured only shallow reductions in Ts; however, during and after rainfall events, tagged birds remained inactive in their burrows during the daytime and employed bouts of torpor that were relatively deep (min. Ts: 18.8°C) and long (max.: 17.5 h). The depth of torpor and extension of torpor beyond the nocturnal rest phase expand the known capabilities for heterothermy within passerine birds. For aerial foraging swallows, torpor is presumably an important adaptation for reducing starvation risk during weather events that reduce prey availability. Our findings have implications for understanding avian thermoregulatory strategies, the evolution of torpor, and how endothermic animals cope with extreme weather events. They also highlight the power of biologging to reveal previously unknown physiological capabilities and provide insight into the adaptive importance of animal responses to natural environmental conditions.

Farming practices induce contrasted effects on parasitic infections in passerine birds in agricultural landscapes

Measurement of Corticosterone Metabolites in Droppings of Small Passerine Birds: a Noninvasive Method for Assessing HPA Axis Activity

Interactions between urbanization, malaria infection and avian cloacal microbiome.

Seasonal fluctuations significantly impact bird species diversity and community composition. This study was conducted in the eastern Rapti river, Nepal during winter and summer seasons to explore bird diversity in different seasons. The line transect method was adopted for this study. Altogether 21 transects were placed, and 110 bird species were recorded. According to the Shannon-Weiner diversity index, greater avian richness and diversity was recorded in the winter season than the summer season. In contrast, bird species were evenly distributed during the summer season than the winter season. The order passeriformes, and guild insectivorous had the highest number of bird species, and resident species were the most prominent. One of the notable sightings in this study was the record of Watercock (Gallicrex cinerea) for the Makwanpur District, Nepal. This study provided an overall checklist of bird species in the region, laying out baseline data on the area’s avifauna to aid and guide future studies. The Eastern Rapti river provides a unique habitat for bird species and requires a conservation management plan to protect the birds and their habitat.

Wild waterfowl and shorebirds are the primary reservoir of influenza A viruses in nature. The role of wild birds from other taxonomic groups remains insufficiently studied or is a subject of debate. This applies in particular to Passeriformes, the most diverse avian order, accounting for approximately 60% of the global bird population, where the role in circulation of influenza A viruses is underexplored. We used serological, virological, and PCR-based methods to survey avian influenza viruses in Passeriformes birds (65 species, 20 families) in Ukraine over a 20-year period, 2004–2025. Antibodies to influenza viruses were detected in serum and egg yolk of seven passerine species, with average seroprevalence 1.24% in sera and 8.94% in yolk samples. Seroprevalence varied across species, ranging from 1.96 to 27.2%. Virological screening resulted in the isolation of two viruses from Fieldfares (Turdus pilaris) of the subtypes H1N1 and H7N1. The overall infection rate based on virus isolation was 0.15%, while local infection rate in Fieldfares reached 11.1%. According to PCR results, 41 positive samples were detected, representing 3.61% of all tested birds (ranging from 1.42–9.1%), and by location ranged from 6.25–9.1%. Sequencing and phylogenetic analyses of H1N1 (Fieldfare), H7N1 (Fieldfare), H3N8 (Great Tit Parus major) influenza viruses confirmed them as Eurasian lineage low pathogenic avian influenza viruses and with close relatedness to viruses of the same subtypes circulating among wild waterfowl.

ABSTRACTEnvironmental contamination alters ecological interactions among organisms, including those associated with parasitism. Contaminants can mediate parasitic relationships at multiple scales by changing host vulnerability to infection and disrupting transmission‐relevant contacts. The overall effect of contamination on parasitism remains poorly understood, yet the interplay between these stressors has significant implications for animal and human health. We conducted a community‐scale field study to evaluate whether trace element contaminants derived from coal combustion residuals and nuclear fission products alter the dynamics of haemosporidian blood parasites, dipteran vectors, and avian hosts in riparian and wetland habitats in South Carolina, USA. We captured 329 individuals of 31 passerine bird species and 195 Culex mosquito vectors at two sites affected by coal combustion waste, two sites affected by nuclear fission waste, and two reference sites. We evaluated whether blood concentrations of zinc, copper, mercury, and selenium and whole‐body radioactivity concentrations because of cesium‐137 predicted the likelihood of single and coinfections by Plasmodium, Haemoproteus, and Leucocytozoon within passerine hosts. We also evaluated whether the likelihood of Plasmodium infection in Culex vectors differed with the presence of site‐level contamination. Individual passerine hosts inhabiting coal combustion waste sites had significantly higher blood selenium concentrations than those at reference sites, and blood selenium was negatively associated with the likelihood of Leucocytozoon infection. The likelihood of infection with Plasmodium did not vary between vectors at contaminated versus reference sites. The transfer of low‐dose, waste‐derived selenium to wildlife may bolster individual response to some parasites and increase the reservoir capacity of host populations. Our findings highlight complex effects of trace elements on wildlife disease dynamics and reveal priorities for future research in contaminated habitat.

Seasonal adjustments of basal metabolism and substrate metabolism in an Asian passerine bird, the red-billed leiothrix.

Bird songs are typically associated with mate attraction and territorial defense behaviours. Some passerine birds sing two categories of songs, primary and flight songs, that vary in song rate and complexity and may vary in function. LeConte's sparrow Ammospiza leconteii is one of the least studied North American passerines; despite several descriptions of flight songs, the vocal behaviour is poorly described. We used a passive acoustic monitoring dataset (PAM) from northwestern Ontario, Canada, to describe the structure of LeConte's sparrow flight songs and to determine whether song type use varied with time of day and/or season We identified songs that included extra elements in addition to the primary song that match the description of a flight song. The flight song was less likely to be sung than primary song at all periods of the day. The probability of singing and amount of both primary and flight songs varied significantly with period of day and calendar date, with the two song types showing different seasonal patterns among diel periods. We found no clear temporal partitioning of types, although the diel period in which each song's activity peaked differed. We found flight songs were most frequent in the evening or early dusk chorus. After evening civil twilight, LeConte's sparrows did sing at late dusk and at night, suggesting they are regular nocturnal singers, particularly early in the breeding season. The probability of singing in the morning declined with date, and song rates and probability of singing were higher at dawn than after sunrise. Thus, surveys targeting LeConte's sparrow should be conducted early morning, beginning before sunrise and in June to confirm presence. We hope that future PAM recording paired with focal recording of individuals can be used to examine variation in the structure of flight songs within and among individuals and populations.

Background:West Nile virus (WNV) is maintained in an enzootic cycle between reservoir host birds and Culex (Cx.) spp. mosquitoes. This relationship presents a potential target for vector control strategies. Ivermectin (IVM), an endectocidal drug that selectively affects invertebrates while remaining safe at high concentrations in mammals and birds, can be delivered to Cx. tarsalis via blood meals from birds fed IVM-treated bird feed. In this study we evaluated the safety, efficacy, and utility of IVM-treated bird feed as a novel vector control strategy by assessing its impact on multiple bird species and mosquitoes.Methods:Mosquitoes were collected during peak WNV transmission season in Northern Colorado and DNA extracted from blood meals to determine host species. Chickens, pigeons, zebra finches, and house sparrows were fed different formulations of IVM-treated bird feed and observed for clinical signs, and their sera were fed to Cx. tarsalis mosquitoes to evaluate mosquitocidal efficacy. Feeding rates and IVM serum concentrations in birds were analyzed by unpaired t-test and one-way ANOVA, and mosquito survivorship was analyzed by Kaplan-Meier curves and compared using paired log-rank tests. IVM serum concentration and mosquito survivorship were compared using Spearman correlation.Results:Speciation analyses conducted on blood meals from Cx. tarsalis collected during peak WNV transmission season in Northern Colorado determined that they feed primarily on songbird species that commonly visit bird feeders, with house sparrows representing the most frequent blood meal host. In laboratory experiments using multiple formulations and doses of IVM, chickens, pigeons, zebra finches, and house sparrows ate comparable amounts of IVM-treated bird feed compared to untreated feed, had similar weight gain, and exhibited no clinical signs of toxicity. Both colony-reared and locally captured Cx. tarsalis showed significant mortality after feeding on sera from IVM-treated birds compared to controls.Conclusions:These results suggest that targeting songbirds with IVM-treated bird feed should be safe for wildlife and may elicit high rates of IVM-induced mortality by reaching a large proportion of WNV vector mosquitoes via their proclivity for feeding on passerine birds.

Climate warming has been associated with widespread body size declines in many vertebrate taxa, but relatively little is known about possible climate warming induced shifts in trait heritabilities. The main goal of the study was to investigate how changing food availability affects evolutionary potential of four traits related to nestlings' body size. We used long-term, pedigree structured data of two woodland passerines living in the boreal zone, the Willow Tit (Poecile montanus) and the Great Tit (Parus major), to study how food availability for their nestlings has changed in time, how this has influenced their morphological traits (viz. wing, tail & tarsus length & body mass) and their heritabilities and evolvabilities. This was done by assessing heritabilities under varying food availabilities using random regression animal models. We found that caterpillar food availability had increased over the 25-year-long study period and that this was accompanied by increases of nestlings' body mass, but not other morphological traits. All traits were heritable in both species, but additive genetic variance, heritability and evolvability were affected by food availability only in the case of the wing length, being higher under low food availability (the Great Tit) or higher under low and high food availability (the Willow Tit). We conclude that changes in food availability seem to have limited influence on evolutionary potential of body size traits in these two passerine birds.

SynopsisThe evolutionary origins of the avian air sac pulmonary system are enigmatic due to the rarity of soft-tissue preservation in fossils. Here, we test whether fine anchoring fibers on the endosteal bone of bird and non-avian dinosaur vertebrae—termed “pneumosteum”—are absent in taxa lacking pneumatic openings. We studied thin sections from the caudalmost cervical and cranial dorsal vertebrae of 21 extant amniotes to infer the presence or absence of invading diverticula through vertebral foramina. We also provide a differential diagnosis of the structural features of pneumosteum. We found that the secondarily aquatic Western grebe (Aechmophorus occidentalis) and Magellanic penguin (Spheniscus magellanicus) lack external pneumaticity and pneumosteum. In addition, the small passerine bird examined (Estrildidae spp.) exhibits invading diverticula but no pneumosteum. This suggests that ventilatory air sacs and associated diverticula can be present despite the absence of osteological and histologic correlates and that these features are lost when transitioning to an aquatic lifestyle or in small-bodied birds. In volant pneumatized birds, diverticula and pneumosteum are associated with pneumatic foramina. This suggests that, in fossil birds, pneumatic foramina are good indicators of the presence of pulmonary diverticula. Furthermore, the loss of invading respiratory diverticula and pneumatic osteological characters in the postcranial skeleton of pursuit diving birds serves as a reminder that adaptation to specific ecologies, such as an aquatic environment, may obscure our ability to reconstruct soft tissue systems accurately in fossil taxa when relying on osteological correlates.