Journal of Thermal Biology

Climate change has altered global climatic conditions, which is affecting the reproductive strategies, offspring development, breeding biology and development of birds. We looked at the impact of different climatic variables (temperature, rainfall and wind speeds) before and during the nestling development phase on nestling development (i.e. nestling hatch weights, nestling growth rates and pre-fledging weights) in the Thorn-tailed Rayadito (Aphrastura spinicauda). We studied two populations. One is situated in a temperate rainforest on the northern border of Patagonia called Pucon which we studied in 2018 and 2019, with mild temperatures (12.5 degrees Celsius), high rainfall (636ml) and low wind speeds (6.3km/h). The other is in a sub-Antarctic old growth forest in southern Patagonia called Navarino island which we studied in 2018, 2019 and 2023, which is comparatively drier (138ml), colder (8.3 degrees Celsius) and has higher average wind speeds (16.6km/h). Embryonic development is key in ensuring individual future fitness. It is important that this is not interrupted and individuals are therefore vulnerable to damage during early development and it can have carry over effects into adulthood. Exposure to extreme climatic conditions can interrupt this development. Therefore, we expect to find that the climate during incubation to be important in predicting nestling hatch weights, growth rates and pre-fledgling weights. Climatic conditions are known to effect nestling development and extremes in climatic conditions have negative consequences on nestling development. We therefore expect that highly variable climatic conditions will have a negative effect on nestling development. We analysed populations separately because we expect populations to have developed different reaction norms to climatic factors. We found in both locations that hatching weights become lower each year, but growth rates and pre-fledging weights are unchanged. In Navarino, medium sized clutches produced the largest hatchlings whilst large and small clutches produced the smallest hatchlings and high or low rainfall during the egg laying and incubation phase produces smaller nestlings. No other climatic factors impacted hatch weights in Navarino. We also found that high or low average ambient temperatures during incubation and early nestling development in Navarino result in lower overall growth rates. Whilst in Pucon, lower rainfall and high or low wind speeds during incubation produce smaller hatchlings, but neither climatic nor biotics factors could explain growth rates in Pucon. We found pre-fledging weights could not be explained by climatic or biotics factors in either location. This is the first study of its kind to examine the environmental drivers of nestling hatch weights in birds in the wild. By better understanding how climate predicts nestling development, we can understand the potential future threats to fitness and development in birds with greater accuracy as conditions continue to change.

Identifying how and why species vary in their ability to adjust to rapidly changing climates is a key challenge in ecology. While phenological shifts are well documented for birds and often studied in the context of tracking resource availability, less is known about the extent to which adjustments in phenology allow populations to track a consistent thermal niche. In particular, there has been little examination of how the extent of phenological thermal niche tracking compares over time versus space; a comparison that has the potential to inform on the underlying mechanisms. Here, we use data on breeding phenology derived from BTO Nest Record Scheme data, to examine the extent to which 13 passerine bird species track a consistent incubation thermal niche across years (both interannually and a year gradient) and along latitudinal and elevational gradients, and whether migrant and resident species differ in their tracking ability. Overall, we found support across species for partial tracking, with all species showing trends consistent with partial tracking across one or more axis, though for one species we could not reject the null hypothesis of no tracking. When we looked at average trends across species, we found significant tracking across interannual variation, latitude, and elevation, but not across a year trend. However, we found no evidence that tracking differs between residents and migrants, and for only a few species did we found evidence that species incubation thermal niche impacts on fitness. Taken together, our findings highlight the extent to which shifts in phenology can allow birds to track a thermal niche in a changing climate. The timing of a thermal niche provides a useful and widely-applicable yardstick to examine how changes in climate will impact on the abiotic conditions that populations experience.

Rapid changes to weather caused by climate change have a negative effect on much of the worlds animal populations and species. Some populations are more vulnerable than others to the effects of climate change, and individuals are particularly vulnerable during early development. Good embryonic development is important for vertebrate species because this can dictate their breeding success and survival rates, and disruptions to this phase can have far reaching fitness effects that can last into adulthood and beyond. We looked at the impact of weather (ambient temperature, rainfall and wind speed) on the embryonic development of thorn-tailed Rayadito (Aphrastura spinicauda) at two different latitudes in Patagonia, Chile. We measured the heart rate of embryos just before hatching using an egg buddy machine to determine embryonic development. Optimum development of nestlings is important for fledging, so it is essential that embryonic development is successful. We studied two populations. One is situated in a temperate rainforest on the northern border of Patagonia called Pucon which we studied in 2018 and 2019, with mild temperatures (12 degrees Celsius), high rainfall (636ml) and low wind speeds (6.3km/h). The other is in a sub-Antarctic old growth forest in southern Patagonia called Navarino island which we studied in 2018, 2019 and 2023, which is comparatively drier (138ml), colder (8.3 degrees Celsius) and has higher average wind speeds (16.6km/h). We found that embryonic development was better in the south compared to the north, indicated by higher embryo heart rates near hatching in the south. Development of embryos in the northern site was slower when conditions were cold and windy. Development of embryos in the southern site was unaffected by temperature, rainfall or wind speeds. In northern Patagonia, when minimum temperatures were low and wind speeds high during the period encompassing clutch completion, initiation of full incubation and during incubation, have a negative impact on embryonic development. In contrast, when Rayaditos in the southern population experience slow embryonic development, they extend the incubation period allowing embryos more time to develop before hatching. Our study shows that in the north of Patagonia embryonic development declines over years and that Rayaditos seem not to have adapted to dealing with climate change. On the other hand, in the south of Patagonia, embryonic development is unaffected by climatic factors, suggesting that Rayaditos are adapting to climate change through extending their incubation periods, allowing embryos to fully develop before hatching. It appears that Rayaditos in the northern population are not extending their incubation periods and are not adapting to the threats posed by climate change. To our knowledge, this is the first study of its kind to examine embryonic development in the field and to associate this to changing weather patterns whilst highlighting specific days on which development is influenced.

O_LIPhenological shifts are a major ecological consequence of climate change, yet studies often focus on single life stages meaning that the potential for carryover effects between life stages remains poorly understood. Failing to account for these effects may lead to inaccurate estimates of phenological shifts, with consequences for predicted synchrony among interacting species. This is especially relevant for temperate systems where climate warming is occurring unevenly across the year. C_LIO_LIHere, we investigated how temperature experienced the previous autumn and winter (during the pupal and egg stage) influences spring phenology in the winter moth (Operophtera brumata), a herbivorous insect with distinct life stages. Using 50 years of local climate data to create five experimental temperature regimes, we first quantified phenotypic plasticity in the duration and temporal variability of pupal and egg development. We then examined how timing of adult moth emergence affects timing of offspring hatching. C_LIO_LIWe found divergent effects of temperature on different life stages; pupal development time was shortest at intermediate temperatures while egg development time decreased linearly with increasing temperature. Furthermore, phenological shifts due to the conditions experienced by the mother were carried over to influence the phenology of her offspring. While this carryover effect was partially compensated during subsequent stages, compensation decreased under warming conditions. C_LIO_LIThese results refine our understanding of the sensitivity of the annual cycle of winter moth phenology to variation in temperature with potential implications for population dynamics and interspecific interactions. Overall, our findings highlight the need to consider the impacts of warming across multiple life stages so that carryover effects can be properly accounted for. Doing so will improve predictions of phenological shifts under future climates. C_LI

O_LIEctotherms in thermally variable environments mediate energy expenditure through both physiological and behavioural responses. However, many studies focus on constant temperature acclimation, and few consider behaviour and physiology in unison. It is unclear how acclimation to thermal variability affects locomotory choices, activity timing, and performance across daily thermal cycles. C_LIO_LIWe investigated the effects of thermal variability in the temperate dung beetle Onthophagus taurus. Following acclimation to a low amplitude (22{degrees}C {+/-} 2{degrees}C) or a high amplitude (22{degrees}C {+/-} 10{degrees}C) temperature regime, we measured behaviour and metabolic rate across temperatures. We hypothesised that O. taurus adjusts its locomotive strategy and search window when kept in high amplitude fluctuating temperatures to reduce energy loss associated with high temperature exposure. C_LIO_LIWe found that differences in energy expenditure were determined by propensity for flight which differed between acclimation treatments, particularly at intermediate temperatures. We also found that, following acclimation to a high amplitude of thermal variability, O. taurus exhibited a greater intensity of activity over a narrower window of time, and O. taurus acclimated to a low amplitude of thermal variability showed nocturnal activity. C_LIO_LIWe then used the data to model activity through the growing season over five years. Biophysical models were built using NicheMapR Microclimate and Ectotherm functions to test the length of potential searching time across seasons, the temperatures individuals are exposed, and locomotive strategy. Model outputs showed that acclimation to higher amplitudes of thermal variability increased accumulated degree-hours of activity relative to the low variability acclimation group. Individuals acclimated to higher amplitudes of thermal variability showed greater accumulated degree-hours in spring and fall, but exhibited shorter periods of activity during summer, with the model predicting increased opportunities for flight. Comparatively, O. taurus from the low variability acclimation treatment showed increased night activity in summer but did not fly. C_LI

Climate warming alters the thermal environment experienced by ectotherms, whose physiological performance and fitness are constrained by temperature. Early life stages are often the temperature-sensitive phases of the life cycle, with potential consequences for population persistence, particularly in freshwater stenotherms such as the Arctic charr (Salvelinus alpinus). The persistence of populations will partly depend on the adaptive potential of critical life stages to environmental changes. In this study, we used a common garden approach to compare the response and phenotypic plasticity of four charr populations to warmer conditions. These populations inhabit thermally contrasted lakes and differ in origin (native/introduced) and management history. We reared embryos at either an optimal (5{degrees}C) temperature for larval development or a warmer but realistic (8.5 {degrees}C) temperature. We tested adaptive divergence among populations in four traits (survival, incubation duration, body length and yolk sac volume), using Qst - Fst comparisons. We report negative effects of temperature on body size, survival and earlier hatching. Thermal reaction norms differed among populations, indicating adaptive divergence. Contrary to expectations, populations originating from warmer environments did not consistently exhibit higher trait values under elevated temperatures. In contrast, the unmanaged and colder high-altitude population exhibited higher survival rates and lower yolk reserves for a given size under heat stress than the other populations. Our results suggested that evolutionary trajectories specific to each population are shaped by factors related to the populations history, including introductions, demographic fluctuations and long-term repopulation practices, which can jointly influence the potential for adaptation to heat stress.

O_LIThe frequency and intensity of heat events is increasing across marine and terrestrial ecosystems. Within the same ecological community, the relative exposure and sensitivity to heat stress may vary considerably among interacting species, like predators and prey. This can be especially true for species that interact at the aquatic-terrestrial interface, as well as for interactions between primarily nocturnal and diurnal species, making it difficult to predict how such communities will respond to habitat warming. C_LIO_LIThermal limit metrics such as CTmax are often assumed to equate with ecological death because such temperatures impair behavioral activity and/or physiological functioning. Prey that are diurnally active can be more frequently exposed to temperatures that approach CTmax compared to their nocturnal predators, which may use thermal refuges during the day. Yet the impacts of daytime heat exposure on nighttime predation risk remain unknown. C_LIO_LIHere, we compared the thermal environment, performance, and heat tolerance between the predatory blue crab, Callinectus sapidus and one of its prey species, the mangrove periwinkle Littoraria anguilifera in a tropical mangrove ecosystem. We examined how exposing prey to heat stress at and below their CTmax affected their capacity to avoid predation in the field at night when predation risk is highest. C_LIO_LIWe found that acute exposure to temperatures near CTmax during the day increased the prey species susceptibility to predation during recovery at night. Although both interacting predator and prey have high thermal tolerance, prey are exposed to conditions that already reach CTmax, suggesting that current extremes in temperatures may already be influencing vulnerability to predation in this ecosystem. C_LIO_LIOur results suggest that differential exposure to sublethal heat stress in diurnal prey relative to their predator, along with the subsequent impact of these exposures on predation risk, will play a role in shaping these interacting as climate warms. C_LI

Populations of the same species inhabiting distinct geographical regions must meet the requirements of local thermal regimes to survive. While individuals integrate both deeply conserved and genotype-specific transcriptional responses to temperature shifts, unique local requirements may diversify the balance between these two mechanisms in distinct populations. The sea anemone Nematostella vectensis inhabits highly variable estuarine environments across a broad geographic range, providing an excellent system to investigate how local adaptations shape responses to temperature stress. While studies have explored the genotypic and phenotypic diversity among N. vectensis populations, the diversity in transcriptional responses to heat and cold remain poorly understood. We used RNA sequencing to characterize transcriptional programs in N. vectensis from Nova Scotia (NS), Maryland (MD), and Florida (FL) under acute temperature treatments at 10{degrees}C and 38{degrees}C. Individuals exhibited a stronger response at 38{degrees}C than at 10{degrees}C, with NS and MD responses being similar and FL exhibiting a unique response. A core set of genes was differentially expressed across all populations under heat stress, while responses to cold were highly population specific. To evaluate the role of a key transcription factor, heat shock factor (HSF), we analyzed the presence of HSF binding sites (HSEs) in promoters of differentially expressed genes (DEGs). Upregulated genes containing three or more promoter HSEs were strongly induced at 38{degrees}C in MD and FL, but not in NS. To identify the involvement of other transcription factors, we searched for overrepresented motifs in the promoters of the top 100 DEGs at 38{degrees}C, revealing a differential enrichment of motifs across the three populations. Together, these findings suggest that N. vectensis populations utilize diverse transcriptional programs in response to common hot and cold temperatures.

Because hypoxia and low temperature independently alter metabolism and reproductive investment, their interaction provides a tractable framework for testing whether combined stressors produce non-additive physiological and reproductive effects. Here, we investigated the single and combined effects of hypoxia and low temperature in Drosophila melanogaster across multiple genetic backgrounds. We quantified metabolic rate, thermal tolerance, body mass, fertility, oogenesis progression, and oocyte apoptosis to assess organismal responses to environmental stress. Hypoxia generally increased respiratory quotient and body mass, but its effects on thermal tolerance and fertility were highly genotype dependent. Across traits, combined stressors frequently produced responses that differed from those observed under single stressors, including reduced fertility, altered oogenesis, and changes in oocyte cell death. Importantly, these effects were not uniform: some genotypes exhibited increased oocyte production or reduced cell death under combined stress, highlighting pronounced genotype-dependent differences in stress sensitivity and reproductive allocation. Together, our results demonstrate that the interaction between hypoxia and temperature can modulate metabolic and reproductive responses in ways that are not predictable from single-stressor responses alone. These findings highlight the importance of incorporating genetic background and interacting environmental stressors when evaluating organismal tolerance and adaptive potential under ongoing environmental change.

Dauer larvae are a dormant developmental stage in nematodes that is induced by a range of environmental cues. The molecular mechanisms that transduce these cues to regulate dauer entry have been well characterized in Caenorhabditis elegans, whereas those in other nematode species remain unclear. The closest known sibling species of C. elegans, Caenorhabditis inopinata, occupies a distinct ecological niche and shows an extremely low frequency of dauer formation by starvation in laboratory conditions, suggesting that it could serve as a useful comparative model for analyzing dauer-inducing mechanisms. To support such analysis, we generated a fluorescent dauer reporter, Cin-col-183p::mCherry, in C. inopinata based on a previously reported dauer-specific reporter in C. elegans. This reporter showed fluorescence specifically in the pre-dauer and dauer stages, but not in other developmental stages, indicating that it functions as a dauer-specific marker in C. inopinata. Using these marker strains, we compared the responses to high temperature and RNAi-mediated knockdown of insulin/IGF-1 pathway genes (daf-2, age-1, and pdk-1), and found that dauer induction differs mechanistically between C. elegans and C. inopinata. This dauer-specific fluorescent strain will be a useful tool for investigating the diversity of dauer-inducing mechanisms across nematode species. Article SummaryDauer is a dormant developmental stage in nematodes induced by environmental stress. Although its regulation is well studied in Caenorhabditis elegans, the mechanisms in other species remain unclear. Here, we developed a fluorescent dauer reporter, Cin-col-183p::mCherry, in Caenorhabditis inopinata, a close relative of C. elegans. The reporter was specifically expressed in pre-dauer and dauer stages, confirming its usefulness as a dauer marker. Using this strain, we found that responses to high temperature and insulin/IGF-1 pathway gene knockdown differ between C. elegans and C. inopinata. This reporter will help reveal diversity in dauer-inducing mechanisms across nematode species.

Linking animal movements to environmental drivers is essential for understanding ecological processes and anticipating species responses to climate change. We investigated habitat-specific movements in a globally significant aggregation of loggerhead turtles (Caretta caretta) nesting in Cabo Verde. Satellite tags on 15 adults (12 females, 3 males) provided multi-year tracks spanning breeding, migration, and foraging habitats. Movements and phenology differed by habitat. During the breeding season, females used either coastal areas, remaining within [~]20 m depth, or undertook long looping forays up to 360 km. Males showed two strategies: two remained resident in Cabo Verde waters, including Fra, the largest male tracked (Curved carapace length of 105 cm compared with a male mean of 90.7 {+/-} 10.3 cm), while the third migrated annually to distant foraging grounds and returned ahead of the subsequent breeding season. In foraging habitats, turtles adopted neritic or oceanic strategies: neritic turtles remained localised in warm, productive waters, whereas oceanic turtles ranged widely in deeper, less productive areas. Time- and space-shift analyses showed that oceanic foragers used intermediate sea surface temperature and chlorophyll-a conditions relative to nearby or temporally shifted alternatives, consistent with movement within a thermal-trophic trade-off. Together, these results show how sex, body size, and energy balance drive habitat-specific movement dynamics in a changing ocean.

Nocturnal migration is a remarkable phenomenon observed in many insect species, including moths. Migratory moths are capable of maintaining precise directional orientation during migration, as demonstrated in both laboratory and field studies, suggesting that they use multiple environmental cues for orientation and navigation. Recent studies on Australian Bogong moths revealed that these animals can use stellar cues and likely the geomagnetic field (in conjunction with local visual cues) to select and maintain population-specific migratory direction. However, the underlying orientation mechanisms used by most other migratory moths are still largely unresolved. Further, it remains unclear whether migratory moths can adjust their orientation using Earths magnetic field parameters for determining their position relative to the goal (i.e. location or map information) - an ability clearly shown in some migratory birds which respond to virtual magnetic displacements by correcting their orientation (experiments when animals are exposed to magnetic cues corresponding to other geographic locations). Here, we present results from virtual magnetic displacement experiments conducted on red underwings (Catocala nupta). In addition, we tested their orientation under simulated overcast conditions and in a vertical magnetic field to get indications whether this species relies on geomagnetic or celestial cues to maintain its population-specific migratory direction. Our results show that (1) red underwings did not compensate for virtual magnetic displacement, indicating the absence of a magnetic map; (2) they remained significantly oriented in the absence of geomagnetic information, suggesting the use of a stellar compass; and (3) there was no evidence of magnetic compass orientation in absence of any visual cues.

Organisms must be able to maintain the ability to produce high quality offspring despite experiencing stressful conditions. It is unknown how C. elegans maintain the ability to produce offspring during moderate temperature stress just below the range of temperature that cause sterility. We evaluated apoptosis, fertility, and several progeny fitness metrics in no-apoptosis, high-apoptosis mutants, and in wild strains that varied in their fertility level during moderate temperature stress to understand if apoptosis is a strategy C. elegans use to maintain the ability to produce offspring during a moderate temperature stress. We found that apoptosis mutants were less fertile with less fit progeny compared to wild type under a moderate temperature stress. Wild strains isolated from the environment showed variability in the increase in apoptosis, levels of fertility, and measurements of progeny fitness observed. We also found that an intermediate induction of apoptosis trended with higher fertility and progeny fitness in wild strains under a moderate temperature tress. These results suggest that apoptosis within an optimal range in the C. elegans germline is a strategy used to maintain the ability to produce high quality offspring despite experiencing a moderate temperature stress. Many species also have germline apoptosis, so apoptosis may be a strategy other species use to maintain their own fertility when experiencing stress conditions

Many marine invertebrates are characterized by broad and highly plastic thermal limits, though the dynamic molecular mechanisms that enable extended thermal acclimation remain poorly understood. A classic example is the green crab (Carcinus maenas), which is a prolific and damaging non-indigenous species. Using a 22-day thermal exposure to cold (5{degrees}C), ambient (13{degrees}C), or warm (30{degrees}C) temperatures, we characterized plastic shifts in C. maenas performance using respirometry and time-to-right. We then used untargeted metabolomics and lipidomics analysis of heart tissues from days 4 and 22 to identify the molecular mechanisms underpinning plastic responses over time. Crabs at 30{degrees}C exhibited higher oxygen consumption rates than counterparts at 5{degrees}C. Interestingly, oxygen consumption rate increased over time at both temperatures, indicating thermal plasticity of aerobic respiration. Temperature-dependent metabolic reprogramming was employed by crabs to sustain aerobic respiration across temperature. Catabolism of branched-chain amino acids was important for energy production at elevated temperatures, while catabolism of arginine may have sustained the minimal energy needs of crabs exhibiting metabolic depression at cold temperatures. Righting response was positively correlated with temperature, and did not exhibit any changes over time. Lipidome remodeling consistent with homeoviscous adaptation could have enabled motor activity across temperature. Higher abundances of saturated and monounsaturated lipids likely provided structural integrity to cell membranes at 30{degrees}C, while lower abundances of these compounds may have enabled membrane fluidity at 5{degrees}C. Our work demonstrates the importance of ongoing molecular reprogramming in long-term acclimation, even when whole-animal physiology remains relatively stable. Summary StatementThis study demonstrates how the highly invasive green crab regulates metabolite and lipid pathways over time to maintain physiological performance across different temperatures.

Mediterranean Basin, one of the most important hot spots for reptiles, is also expected to experience significant impacts with climate change, posing a severe risk for the herpetofauna of the region. This study uses the snake-eyed lizard Ophisops elegans as a model organism to investigate the potential impacts of past and future climate change on reptile distributions in the region. An ecological niche model (ENM) was developed with the Maxent algorithm, with location points from GBIF and bioclimatic variables from the CHELSA dataset, then projected onto past LGM ([~]21 kya) and future (2071-2100 SSP3-7.0 and SSP5-8.5) scenarios. Results show that the present-day distribution of O. elegans is primarily driven by temperature seasonality and precipitation, indicating a preference for coastal Mediterranean climates with dry summers. The LGM projection suggests a fragmented and contracted range, confined to coastal refugia around the Mediterranean and Caspian Seas. Future projections for 2071-2100 show consistent and alarming contraction of suitable habitats under both SSP scenarios. In conclusion these findings indicate that O. elegans is vulnerable to significant habitat loss under projected climate change. This severe impact on a wide-spread species implies that the herpetofauna of the Mediterranean Basin may face a significant threat in future.

Artificial light at night is a rapidly increasing driver of global change, affecting both astronomical observations and biodiversity. Regulations such as the Canary Islands "Sky Law" were designed to protect astronomical observations by controlling light intensity and spectral composition, yet their ecological effectiveness remains largely untested. Here, we experimentally assessed whether lighting conditions permitted under this law influence the behaviour of two sensitive nocturnal taxa: seabirds and bats. Field experiments were conducted in Tenerife, Canary Islands, using controlled lighting treatments that varied in intensity (low vs. high) and spectrum (PC amber ~1800K vs. white ~2700K), including a no-light control. We monitored the behaviour of breeding adult Corys shearwaters (Calonectris borealis) using GPS tracking and passive acoustic recording, and quantified bat activity through ultrasonic detectors. Behavioural responses included flight characteristics, colony attendance, vocal activity in shearwaters, and species-specific movement and feeding activity in bats. Generalised linear mixed models were used to evaluate treatment effects while accounting for environmental covariates. Across 211 shearwater flights and extensive acoustic datasets, we found no consistent or significant effects of light treatments on seabird flight behaviour, vocal activity, or bat movement and feeding activity. Instead, environmental variables such as moonlight, seasonality, and interannual variation were stronger predictors of behavioural responses. These results suggest that lighting conditions currently permitted under the Sky Law may have limited ecological impact on the studied taxa under the conditions tested. Further research in less disturbed environments and with broader spectral contrasts is needed to better assess the ecological implications of astronomically motivated lighting regulations.

Sentinel behaviour occurs when individuals use raised positions to scan for predators while the rest of the group forages. Here, we investigated whether a colonial cooperatively breeding species that forages in large groups, the sociable weaver, Philetairus socius, displays sentinel behaviour. This behaviour has been reported in species with similar ecology, behaviour and foraging habits, (e.g. ground foraging in open habitats where aerial predators are common) and, hence, we expected that it could occur in sociable weavers. On the other hand, sentinel behaviour appears to be less common in species that live in very large groups. We used an experimental set-up consisting of an artificial feeding station and perches to assess occurrence of sentinel related behaviours: (i) perching events > 30s on an elevated position, (ii) head-movements and (iii) alarm calling. Birds were seldom observed perching while others fed, and those that did, perched for periods that were too short to be considered as sentinel behaviour (less than 5s on average). Our results suggest that this behaviour is uncommon or even absent in sociable weavers. We discuss whether other factors such as foraging in very large groups, or interspecific foraging associations might make sentinel behaviour less important in this species.

Capturing and handling wild animals is essential for ecological and evolutionary research, yet their effects on physiology, behaviour, and reproductive success remain poorly understood. We investigated short- and longer-term consequences of a capture-handling-restraint protocol in wild great tits (Parus major) over three breeding seasons. To assess short-term responses, we measured circulating corticosterone, a metabolic hormone that responds to unpredictable challenges, and automatically recorded provisioning behaviour. We also explored whether environmental and individual traits were related to provisioning latency (i.e., time to resume provisioning after capture). To evaluate longer-term effects, we monitored provisioning in the days following capture and related it to reproductive success (fledgling number and body condition). We predicted that longer handling would increase stress-induced corticosterone and provisioning latency, that these variables would be positively correlated, and that higher corticosterone and longer latencies would be associated with lower reproductive success. After capture, great tits showed elevated corticosterone and delayed provisioning. Contrary to our predictions, handling duration was negatively associated with stress-induced corticosterone in males (but not females) and did not affect provisioning latency. Provisioning latency was unrelated to corticosterone, environmental, or individual variables. Following capture, parents resumed provisioning, and short-term responses had little influence on reproductive success. We show that parental behaviour and physiology are affected by capture restraint protocols on the short term, but offspring condition and survival are not. However, these results should be interpreted cautiously, as our study lacks an uncaptured control group. Our findings highlight that evaluating welfare impacts requires rigorous study design incorporating both immediate and longer-term behavioural and fitness effects.

The Mediterranean fruit fly (medfly) (Ceratitis capitata (Wiedemann, 1824) is a major agricultural pest, and egg desiccation is a critical constraint during handling and mass-rearing, as even short periods without moisture may compromise developmental success and downstream adult performance. The Wolbachia-medfly symbiosis is a relatively recently established artificial association, generated less than three decades ago using Rhagoletis cerasi as the Wolbachia donor. In this study, we evaluated the effects of egg-stage desiccation on developmental success and subsequent adult performance in three medfly lines differing in Wolbachia status: the uninfected Benakeion line, the wCer2-infected 88.6 line, and the wCer4-infected S10.3 line. Eggs were exposed to desiccation for 0-24 h at 4-h intervals before transfer to larval diet, and hatching, pupation, and adult emergence were recorded. We additionally assessed adult survival under stress for flies emerging from the 0, 8, and 10 h egg-desiccation treatments. Under control conditions, Benakeion showed the highest hatching and developmental recovery, S10.3 the lowest, and 88.6 intermediate performance. Across all strains, short desiccation exposures were comparatively well tolerated, whereas prolonged exposure sharply reduced hatching, pupation, and adult emergence, with the clearest decline at 20-24 h. Strain-dependent differences were expressed mainly at the hatching stage, while later developmental transitions were more similar among strains once larvae had hatched. In the adult follow-up, strain, rather than moderate egg-stage desiccation, was the main determinant of short-term survival and survival under extreme stress, with S10.3 again showing the weakest performance. These results indicate that Wolbachia-associated fitness costs in medfly are strain dependent and that egg-stage desiccation primarily acts at the embryonic bottleneck. Beyond providing insight into the Wolbachia-medfly artificial symbiosis, our findings are directly relevant to egg-handling and strain-evaluation protocols in medfly mass-rearing systems.

Terrestrial Laser Scanning (TLS) captures fine-scaled three-dimensional measurements of ecosystem structure, supporting monitoring of the Essential Biodiversity Variables (EBVs). Yet employing TLS across landscapes remains challenging in remote and topographically complex areas. Remote sensing provides a potential pathway for upscaling TLS-derived structural metrics, but to what extent is unquantified particularly in heterogenous environments, like oceanic islands. Here, we investigated the ability of remote sensing to estimate TLS-derived habitat structure across three contrasting habitats (lowland rainforest, montane cloud forest, and subalpine summit scrub) on La Reunion island. Sentinel-1, Sentinel-2, and Aerial LiDAR (ALS) data were acquired over plots where TLS was completed. We derived defined indices of backscatter coefficients, vegetation indices, and LiDAR metrics and assessed their alignment with TLS measurements using a Procrustes analysis. Subsequently, we used General Additive Models to estimate TLS habitat structure from remote sensing variables. Sentinel-2 exhibited the highest multivariate alignment with TLS (r = 0.51). TLS measurements of horizontal and vertical structure were estimated with the highest cross-validated predictive accuracy (R2 0.39 - 0.73), whilst structural complexity metrics were estimated with greater difficulty (R2 0.02 - 0.20). Multi-sensor models outperformed all single-sensor models in prediction estimates. Model performance also varied across habitats, with the highest agreement between predicted and observed values in the lowland rainforest (r = 0.38), and the lowest agreement (r = 0.35) in the montane cloud forest. Yet the dominant structural feature of each habitat was most accurately captured with remote sensing. Our results demonstrate the potential of integrating multi-sensor remote sensing data to upscale key dimensions of TLS-derived ecosystem structure but remains challenging for fine-scale structural complexity. These findings highlight both the potential and constraints of remote sensing for developing scalable, long-term monitoring frameworks for EBVs, especially in structurally complex and underrepresented island ecosystems.