Biology subjects

Salmon, P.

Publications and source records attributed to Salmon, P..

7 recordsLinked to original sources

bioRxiv2026

Broad scale environmental conditions, not urbanisation, explain geographic variation in great tit feather microstructure

Urbanisation imposes novel environmental conditions that can shape phenotypic traits including plumage, yet, its effects on characteristics beyond colouration remain poorly understood. Feather microstructure plays an important role in thermoregulation, protection from solar radiation and waterproofing, and its expression is sensitive to environmental conditions. Here, we quantified feather barbule density, a key component of feather microstructure, in great tits (Parus major) from five urban-rural paired populations across Europe to assess its association with urbanisation, temperature and elevation. We found no significant effects of the urban environment or temperature. However, feather microstructure significantly varied between the studied areas and was positively associated with elevation and ultraviolet B (UV-B) radiation, suggesting a potential adaptive response to variation in solar radiation.

ecology↗

bioRxiv2026

Rapid and divergent changes in the continental-scale organisation of a short-lived songbird's migratory strategy

It is hard to predict how rapidly songbird migration will change in the Anthropocene. Indeed, since songbird migration is thought to have a strong heritable component, the continental-scale organisation of migratory movement might be seen as fairly inflexible. Perhaps one of the best models for the ecology and evolution of migration is the Eurasian blackcap (Sylvia atricapilla) which, as part of a continent-wide effort to characterise blackcap migratory phenotype, we geolocator-tracked from breeding sites in eastern Poland. Rather than migrating in the expected south-easterly migratory direction, these birds migrated south and south-west - suggesting that blackcaps in the east of their range have switched migratory direction. We sought to investigate the extent of this phenomenon using almost a century of ringing data, which confirmed that blackcaps breeding across the entirety of Eastern Europe have indeed almost completely stopped using their historic eastern flyway. Instead, a shorter-distance west-migrating phenotype has emerged, which we find is consistent with warmer winter temperatures opening up wintering sites at more northerly latitudes in the west. We discuss what drives changes in migratory behaviour over short timescales; and consider what this tells us about how migratory information is inherited.

animal behavior and cognition↗

bioRxiv2026

The road to nowhere: geolocation-by-genotype traces large-scale yellow-browed warbler vagrancy to central Siberia

Vagrant animals - individuals found far outside their normal range - offer powerful natural experiments for understanding migratory mechanisms. The yellow-browed warbler (Phylloscopus inornatus) provides perhaps the best-yet example, typically migrating from Siberia to South/Southeast Asia yet found in increasingly large numbers in Western Europe. This represents a strikingly unresolved evolutionary puzzle: why do so many migrants consistently move in almost the complete wrong direction? A critical first step toward solving this enigma is determining where these birds come from. If vagrants came from the proximal western range edge this would imply simple disorientation, whilst a more easterly origin could imply large-scale reverse misorientation. Here, we develop a geolocation-by-genotype algorithm for low-coverage whole-genome resequencing data collected from feathers. Our method identifies spatially informative SNPs; clusters them to account for covariance in allele frequency through space; and employs a bootstrapped maximum-likelihood framework to estimate spatial origin with uncertainty. Applied to more than 80 European-caught birds, our results place their origin in central Siberia (118{degrees}E; 89-134{degrees}E [95% CI]); over 2000km east of the western range edge. These results suggest mass misorientation in a near-reverse direction, and highlight the yellow-browed warbler as an exceptional system for probing the mechanism, ontogeny and evolution of migration.

animal behavior and cognition↗

bioRxiv2025

Experimental evidence for reproduction to increase mitochondrial respiration, but decrease mitochondrial efficiency, in females of a short-lived bird

Reproduction is generally considered as one of the most energy-demanding processes, causing a trade-off with survival. Although this "cost of reproduction" plays a pivotal role in theory on ageing and life-history evolution, the physiological mechanisms underlying it remain largely unresolved. As mitochondria synthesize 90% of the energy available to eukaryotic cells, their functioning may be crucial in mediating the cost of reproduction. In this study, we therefore experimentally manipulated the reproductive status (gamete production) of male and female Japanese quail (Coturnix japonica), and tested for effects on mitochondrial respiration. We found that reproduction led to an overall increase in mitochondrial O2 consumption in females. This was primarily driven by a large increase in proton leak, as O2 consumption for adenosine triphosphate (ATP) synthesis only increased slightly. Hence, reproductively active females had a severely reduced efficiency in ATP production, compared to non-reproductive females. In males, mitochondrial respiration and its efficiency were unaffected by reproduction, and similar to that in non-reproductive females. We suggest the large increase in proton leak in reproductive females to represent an adaptive mechanism to mitigate the production of reactive oxygen species (ROS), and to be an unavoidable consequence of elevated ATP synthesis. The latter would cause constraints on energy availability for reproductive females, and thereby trade-offs with other energy demanding processes, like somatic maintenance. The absence of effects of reproduction on male mitochondrial respiration confirms the general view that gamete production is less costly for males. Significant statementReproduction is one of the most costly biological processes; not only in terms of energy, but also in terms of its effect on survival. Mitochondria, the primary energy sources in eukaryotic cells, may mediate these costs. By experimentally manipulating the reproductive activity of male and female Japanese quail, we demonstrate that female egg production leads to increased mitochondrial oxygen consumption, primarily due to an increase in proton leak, reducing the efficiency in energy production. We suggest the increased proton leak to be an adaptive response to reduce reactive oxygen species production, but to limit the energy available for processes such as somatic maintenance. Male reproduction did not affect mitochondrial function, confirming the general view that sperm production is relatively cheap.

physiology↗

bioRxiv2022

Urbanisation impacts plumage colouration in a songbird across Europe: evidence from a correlational, experimental, and meta-analytical approach

Urbanisation is increasing at a phenomenal rate across the globe, transforming landscapes, presenting organisms with novel challenges, shaping phenotypic traits, and even impacting fitness. Among colour traits, urban individuals are widely claimed to have duller tones in carotenoid-based traits, the so-called "urban dullness" phenomenon. However, at the intra-specific level, this generalisation is surprisingly inconsistent and often based on examples from single urban/non-urban population pairs or a limited geographic area. Here, combining correlational, experimental, and meta-analytical results from a common songbird, the great tit (Parus major), we investigated carotenoid-based plumage coloration in urban and forest populations across Europe. We find that, as predicted, urban individuals are paler than forest individuals. Interestingly, we also find large population-specific differences in the magnitude of the urban-forest contrast in plumage colouration. Moreover, our meta-analysis indicates a non-significant effect of environmental pollution on carotenoid-based plumage for the species, suggesting that the observed differences across urban populations are not only driven by pollution. Finally, using one region as an example (Malmo, Sweden), we reveal population-specific processes behind plumage colouration differences, which are likely the result of variation in the spatial and temporal distribution of carotenoid-rich resources in anthropogenic environments. This is the first study to quantify the consistency of an oft-cited textbook example of the impact of urbanisation on wildlife; our results provide the most convincing evidence to date of the "urban dullness" phenomenon, but also highlight that the magnitude of the phenomenon depends on local urban characteristics.

evolutionary biology↗

bioRxiv2020

"The stressed bird in the hand": Influence of sampling design on the physiological stress response in a free-living songbird

Despite the widely used application of standardized capture-handling protocols to collect blood and assess the physiological stress response, the effect of the actual sampling design (e.g. timing and the number of blood samples) often differs between studies, and the potential implications for the measured physiological endpoints remain understudied. We, therefore, experimentally tested the effects of repeated handling and multiple blood sampling on the stress response in wintering free-living great tits (Parus major). We modified a well-established sampling protocol of avian studies by adding either an additional blood sample or a "sham-manipulation" (i.e. handling associated with the blood sampling procedure without venepuncture), to disentangle the effects of handling stress and blood loss. We combined three different stress metrics along the endocrine-immune interface to investigate the acute short-term stress response: total corticosterone levels (CORT), the heterophil/lymphocyte ratio (H:L), and the Leukocyte Coping Capacity (LCC). Our study provided three key results: i) no relationship between CORT-levels, LCC and H:L, confirming that these three parameters represent different physiological endpoints within the stress response; ii) contrasting dynamics in response to stress by the measured parameters and iii) no difference in stress levels 30 minutes after capture due to one additional blood sampling or handling event. By optimising the sampling design, our results provide implications for animal welfare and planning experimental procedures on stress physiology in passerine species. Summary StatementWhen testing the short-term stress response in free living passerines, both - the scientist and the bird may be better off with a 15-minute stress protocol.

physiology↗

bioRxiv2020

Repeated genomic signatures of adaptation to urbanisation in a songbird across Europe

Urbanisation is currently increasing worldwide, and there is now ample evidence of phenotypic changes in wild organisms in response to this novel environment, but the extent to which this adaptation is due to genetic changes is poorly understood. Current evidence for evolution is based on localised studies, and thus lacking replicability. Here, we genotyped great tits (Parus major) from nine cities across Europe, each paired with a rural site, and provide evidence of repeated polygenic responses to urban habitats. In addition, we show that selective sweeps occurred in response to urbanisation within the same genes across multiple cities. These genetic responses were mostly associated with genes related to neural function and development, demonstrating that genetic adaptation to urbanisation occurred around the same pathways in wildlife populations across a large geographical scale.

evolutionary biology↗