Journal of Avian Biology最新文献

{"title":"Using functionally representative bird species and passive acoustic monitoring to model ecological variation across a land use mosaic in a dryland system","authors":"Frowin K. Becker,&nbsp;Connor M. Wood","doi":"10.1002/jav.03670","DOIUrl":"https://doi.org/10.1002/jav.03670","url":null,"abstract":"<p>Birds, through their wide range of functional traits, can serve as useful indicators of ecological change. Monitoring them across spatial scales has been considerably enhanced through passive acoustic monitoring (PAM) and automated call identification. Reconciling PAM with avian functional ecology remains an underexplored domain and could be a useful ecological assessment tool – especially in dryland ecosystems. In this study, we followed a systematic selection process to identify functionally representative and acoustically compatible bird species across variably managed (fenced-in) land parcels in north-central Namibia. Following this selection process, we identified eight suitable species, and used variables relating to land management, soil and vegetation to construct alternative occupancy models to estimate our selected species' occupancy probabilities across our study area. For five species, models with our ‘core' variables outperformed the null model, with several species distributions influenced by different environmental variables. Our findings demonstrate a quantitative, PAM- and trait-based approach to indicator species selection and the ways in which landscape features can affect the occupancy probabilities of functionally representative bird species. While exploratory in nature, this study can help develop an ecological monitoring concept that not only integrates bioacoustics and trait-based assessments but presents an effective tool for more underrepresented regions.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2026 5","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jav.03670","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148878406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cooperative partnerships in azure-winged magpies transition from kin-based to non-kin-based during the period of colonization of the Qinghai-Xizang Plateau","authors":"Ning-Ning Sun,&nbsp;Miao Cheng,&nbsp;Xiao-Dan Zhang,&nbsp;Li-Fang Gao,&nbsp;Bo Du","doi":"10.1002/jav.03546","DOIUrl":"https://doi.org/10.1002/jav.03546","url":null,"abstract":"<p>Cooperative breeding exhibits considerable variation in the conditions in which it occurs and the relationship between dominant breeders and helpers. To explore factors influencing the dynamics of cooperative breeding, we investigated cooperative breeding in azure-winged magpies <i>Cyanopica cyanus</i> during their colonization of a high-altitude environment. Cooperative breeding occurred more frequently in colonies with higher nesting density, while it did not vary with the environmental proxy (i.e. nest habitat tree-ring index). Those nests with delayed clutch initiation or larger-bodied social males were less likely to adopt cooperative breeding. These results suggest that social factors play a more critical role than natural environmental conditions in driving the occurrence of cooperative breeding. Although both sexes might act as helpers, males did so more frequently than females, and females unrelated to social breeders became helpers more often than unrelated males. The likelihood of helpers unrelated to either parent rose significantly over the period of colonization, suggesting that cooperative partnerships transition from kin-based to non-kin-based over the time of azure-winged magpies' colonization of high-altitude habitats. Accordingly, unrelated helpers gained greater shares of reproductive partitioning compared to those related to one or both parents. Given that azure-winged magpies face high risks of predation from natural predators or conspecific nest-raiders, the higher occurrence of nest predation by predators – but not by conspecific nest-raiding – in biparental nests compared to cooperative groups indicates that cooperative breeding helps reduce predation pressures from natural predators, but not from conspecific raiders. Therefore, cooperative breeding facilitates azure-winged magpies' successful colonization of novel high-altitude habitats.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2026 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jav.03546","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148754070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Birds of prey and the city: variation in immunity and parasites exposure along an urbanization gradient","authors":"Gianluca Damiani,&nbsp;Gábor Árpád Czirják,&nbsp;Gaia Porporato,&nbsp;Nayden Chacarov,&nbsp;Giacomo Dell'Omo,&nbsp;David Costantini","doi":"10.1002/jav.03655","DOIUrl":"https://doi.org/10.1002/jav.03655","url":null,"abstract":"<p>Pathogens are major ecological and evolutionary forces, and the immune system is central to coping with these challenges. Environmental variation, including urbanisation, can alter both pathogen exposure and immune function, making it important to understand how responses vary across habitats. We addressed the impact of urbanization on both immunity and parasite exposure using common kestrel <i>Falco tinnunculus</i> nestlings as our study species. This generalist raptor occurs in both urban and non-urban areas, offering a model to investigate how urban environments affect early-life immunity. Previous studies on kestrels reported baseline immune differences but did not test induced responses, limiting understanding of immune function. We challenged nestlings with phytohemagglutinin (PHA), collecting blood before and 24 hours after injection, and measured six immunological markers: haptoglobin, bacterial killing activity, lysozyme, hemagglutination, hemolysis, and IgY. We also quantified exposure to two types of ecto- and hemo-parasites. PHA induced an inflammatory response, but this response was similar across habitats, indicating that the habitat did not influence the responsiveness to this particular antigen. Baseline innate immunity generally increased along the urbanisation gradient, whereas baseline adaptive immunity (IgY) rose within a season but in a similar way across habitats. Exposure to ectoparasites <i>Carnus hemapterus</i> was significantly higher in natural habitat compared to urban habitat, but did not explain individual variation in the response to the PHA challenge. Exposure to hemo-parasites was negligible, as we found only two out of 108 nestlings positive. Our results suggest that urbanisation does not influence the immune response to an experimental immune challenge. Further studies are needed to determine whether these findings can be generalized to other antigens or live parasites, as well as to populations with differing histories of parasite exposure or habitat conditions.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2026 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jav.03655","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148754018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sampling hour matters: diel variation in leukocyte profile of red-legged partridges","authors":"Daniel Parejo-Pulido,&nbsp;Ana Serrano-Jiménez,&nbsp;Lorenzo Pérez-Rodríguez","doi":"10.1002/jav.03653","DOIUrl":"https://doi.org/10.1002/jav.03653","url":null,"abstract":"<p>Leukocyte counts are widely used as integrative biomarkers of immune function and physiological condition across ecological and biomedical sciences. However, their reliability can be compromised by sources of variation related to practical issues associated with sampling. Here, we investigated whether leukocyte profiles were affected by the hour of sampling in adult captive male red-legged partridges <i>Alectoris rufa</i>. We used a repeated-measures design in which birds were sampled once per week over four consecutive weeks in May. In each weekly sampling session, individuals were sampled at one of four predefined time points across the day (06:00 h – before sunrise –, 10:30, 15:30, 20:00 h, GMT+1). Total leukocyte (WBC) counts and the absolute numbers of all leukocyte types showed pronounced daily fluctuations, with minima at mid-morning and recovery by afternoon or evening. By contrast, relative leukocyte proportions and the H:L ratio were more stable, although eosinophil and monocyte proportions varied significantly across the day. Effect sizes indicated that the strongest diel variation occurred in total WBC counts and the absolute counts of lymphocytes and monocytes. In addition to diel patterns, we detected mainly proportional leukocyte variation across sampling days. These fluctuations likely reflect transient physiological or environmental factors, although their cause remains uncertain. Handling time also significantly affected most leukocyte variables, with longer handling intervals producing rapid changes in the number and proportion of leukocyte types. To minimise potential temporal bias in leukocyte measurements or facilitate its statistical control, we recommend standardising sampling within narrow time windows, recording the sampling hour, and minimizing time elapsed between capture and sampling.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2026 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jav.03653","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148753092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hatching failure in an aerial insectivore, the tree swallow Tachycineta bicolor, is driven by embryonic mortality, not infertility","authors":"Hannah Tench,&nbsp;Nicola Hemmings,&nbsp;Russell D. Dawson","doi":"10.1002/jav.03664","DOIUrl":"https://doi.org/10.1002/jav.03664","url":null,"abstract":"<p>Egg development is a crucial stage in the life cycle of birds, and across wild species up to 17% of eggs fail to hatch under normal conditions. Hatching failure is due to either infertility or embryonic mortality; however, methods to distinguish between these two causes have been underused, partly due to the assumption that eggs must be refrigerated and tested relatively quickly. In 2022 and 2023, we monitored 1090 eggs laid by tree swallows <i>Tachycineta bicolor</i> from 191 nests at three study sites in British Columbia, Canada. Using fluorescence microscopy to identify embryonic and sperm nuclei, we conservatively estimated that 98.3–100% of eggs were fertile, and most cases of hatching failure were therefore due to embryonic mortality, not infertility. Embryonic mortality was most likely to occur during early incubation, before development is usually macroscopically visible. We also used fluorescence microscopy to examine 114 eggs laid by tree swallows kept in long-term frozen storage and found that not only could fertility be assessed, but the fertility rate of these eggs was also close to 100%. To our knowledge, this study is the first to quantify fertility using embryonic nuclei in tree swallows, and provides the basis for further investigation into factors contributing to hatching failure in this species. Our success using frozen eggs for fertility testing is especially relevant for conservation groups and captive breeding facilities that may already have unhatched eggs stored in freezers, or are limited by capacity or funding and need to place eggs in long-term storage until resources are available for testing.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2026 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jav.03664","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148753308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Low levels of extra-pair paternity in the long-lived colonial Alpine swift Tachymarptis melba","authors":"Christoph M. Meier,&nbsp;Giulia Masoero,&nbsp;Maria Burger,&nbsp;Agnes Schärer,&nbsp;Christophe Sahli,&nbsp;Pierre Bize,&nbsp;Gwenaël Jacob","doi":"10.1002/jav.03635","DOIUrl":"https://doi.org/10.1002/jav.03635","url":null,"abstract":"<p>It has been suggested that a high aerial lifestyle makes it difficult for males to limit mating opportunities for their partners. This would explain the particularly high levels of extra-pair paternity (EPP) observed in several species of swallows and martins (Hirundinidae, Passeriformes), but EPP in the other bird lineages with a high aerial lifestyle, such as swifts (Apodiformes), is largely unknown. Here, we investigated EPP in the Alpine swift <i>Tachymarptis melba</i>. We found nine cases of EPP in 9 broods out of 214 (4.2%) nestlings and 87 (10.3%) broods analysed with information on fathers. This low incidence of extra-pair paternities is similar to the only estimate reported so far in Apodiformes (i.e. 4.5% of nestlings in the common swift <i>Apus apus</i>). We suggest that life-history traits (biparental incubation, long lifespan, and frequent mate retention across years), rather than their aerial lifestyle, may explain the low incidence of EPP in swifts.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2026 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jav.03635","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148753063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Migratory nightjars roost on asphalt to reduce thermoregulatory costs and increase fuel accumulation","authors":"Paula Hidalgo-Rodríguez,&nbsp;Pim Edelaar,&nbsp;Julio Rabadán-González,&nbsp;Jairo Robla,&nbsp;Lars Ursem,&nbsp;Pedro Sáez-Gómez,&nbsp;Carlos Molina,&nbsp;R. Mark Brigham,&nbsp;Carlos Camacho","doi":"10.1002/jav.03600","DOIUrl":"https://doi.org/10.1002/jav.03600","url":null,"abstract":"<p>Migration is an energetically expensive event in the annual cycle of birds, requiring substantial fuel stores for successful completion. Optimizing fuel deposition rates benefits migrants, as faster fueling reduces the time required to store the necessary energy, maximizing overall migration speed. Studies on fueling optimization have largely focused on increasing energy intake to generate a surplus. In contrast, the role of reducing energy expenditure has received comparatively little attention. We analyzed an 8-year (2011–2018) dataset collected as part of a long-term field study on a population of the migratory red-necked nightjar <i>Caprimulgus ruficollis</i> in southern Spain to assess roosting-substrate preferences during the fueling period. Specifically, we investigated the influence of intrinsic factors (body mass, food consumption, age and sex of the individuals) and environmental factors (ambient air temperature, time since sunset and moon illumination) on nightjars' use of gravel versus asphalt roads as a thermoregulatory mechanism to reduce overall energy expenditure during fueling. An experiment simulating heat loss for road-sitting nightjars confirmed that asphalt is a more thermally favorable substrate than gravel, enabling roosting nightjars to reduce energy expenditure for thermoregulation. We hypothesized that nightjars may thus benefit from using asphalt roads to obtain a more positive energy balance and potentially facilitate fueling. Using an information-theoretic approach and capture data from 505 individuals, we evaluated support for a set of models which made a priori predictions based on ecological reasoning and previous research. We found that nightjars most often sit on asphalt roads on moonlit nights, regardless of age, sex, body mass, food consumption, time since sunset and ambient temperature. Given that the foraging efficiency of nightjars peaks during moonlit nights, individuals preparing for the migratory journey may benefit from reduced thermoregulatory costs on asphalt during full-moon periods, thereby facilitating faster fuel deposition. Our results highlight the potential importance of behavioral thermoregulation for efficient fueling in migratory species.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2026 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jav.03600","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148753065","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The abundance-centre hypothesis re-examined: body mass, blood glucose, and elevational distributions in Afrotropical forest birds","authors":"Riccardo Pernice,&nbsp;Tomáš Albrecht,&nbsp;Oldřich Tomášek,&nbsp;Ondřej Kauzál,&nbsp;Francis Teke Mani,&nbsp;Esembe Jacques Chi,&nbsp;Matouš Janča,&nbsp;Vincenzo Arizza,&nbsp;Daniela Campobello,&nbsp;David Hořák","doi":"10.1002/jav.03612","DOIUrl":"https://doi.org/10.1002/jav.03612","url":null,"abstract":"<p>A long-standing theory, the abundance-centre hypothesis (ACH), predicts that species peak in abundance at the centre of their geographic range, where environmental conditions are optimal, and decline towards range limits as conditions deteriorate. Yet, tests of the ACH in birds along elevational gradients have yielded mixed results. Moreover, resource availability, rather than abiotic factors per se, may better explain species abundance patterns. Therefore, life-history traits associated with nutritional status could be key to predicting abundance patterns. Along with the ACH, we tested two physiological traits as potential predictors of avian abundance along an Afrotropical elevational gradient: blood glucose concentrations (the abundance–glucose relationship; AGR) and body mass (the abundance–body mass relationship; ABR). We collected abundance, glucose, and body mass data from 51, 15, and 29 free-living species, respectively, within a primary forest on Mt Cameroon (West-Central Africa). Model fits for each species revealed that many species show a monotonic abundance pattern. Logistic models further indicated that high-elevation birds were more likely to increase in abundance with elevation, peaking near the treeline. In contrast, lowland birds tended to decline with elevation, peaking near the lower forest edge. Bayesian phylogenetic multilevel models indicated that neither glucose nor body mass was a strong predictor of abundance. Taken together, our findings provide little support for the ACH and suggest that most lowland and highland species occupy truncated realized niches near forest elevational edges. Although our results do not link avian physiology to population density, we encourage future ecologists and ornithologists to collect larger sample sizes to effectively test the AGR and ABR hypotheses and, thus, elucidate the mechanisms behind variations in species abundances.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2026 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jav.03612","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148752731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Forest degradation reduces acoustic partitioning in tropical avian communities","authors":"Jennifer A. Darby,&nbsp;Oliver C. Metcalf,&nbsp;Jos Barlow,&nbsp;Erika Berenguer,&nbsp;Joice Ferreira,&nbsp;Nárgila Gomes de Moura,&nbsp;Cassio Alencar Nunes,&nbsp;Alexander C. Lees","doi":"10.1002/jav.03662","DOIUrl":"https://doi.org/10.1002/jav.03662","url":null,"abstract":"<p>The acoustic niche hypothesis posits that species partition acoustic space by frequency and time to avoid signal masking, and that any local loss of species leaves detectable gaps in co-evolved soundscapes. However, loss, fragmentation and disturbance of habitat often lead to species turnover, and as sensitive species are lost, generalist species colonise, potentially leading to novel overlaps of acoustic niches. We tested the acoustic niche hypothesis in variably disturbed tropical forests in the Brazilian Amazon by comparing overlapping vocalisations in undisturbed and disturbed forests. We measured the effect of disturbance on the frequency of overlapping vocalisations, then assigned sensitivity scores to each species and modelled how species sensitivity and species richness per sound file impacted overlapping vocalisations. We found that logged forests that have burnt recently had significantly higher rates of vocalisation overlap. Across all disturbance types, overlapping vocalisations were significantly higher when species richness and species sensitivity per 15-s sound file increased. To our knowledge this is the first paper to test the acoustic niche hypothesis in human-modified tropical forests and it provides insight into the impact of disturbance on species' ability to effectively communicate, as well as the utility of passive acoustic monitoring in measuring the responses of avian communities to global change.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2026 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jav.03662","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148467677","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Haemosporidian infections limit physiological adaptation to elevation in birds: evidence from haemoglobin and fat reserves","authors":"Zamekile D. Bhembe,&nbsp;Sara Padidar,&nbsp;Kat Bebbington,&nbsp;Sjouke A. Kingma,&nbsp;Machawe I. Maphalala,&nbsp;Ara Monadjem","doi":"10.1002/jav.03580","DOIUrl":"https://doi.org/10.1002/jav.03580","url":null,"abstract":"<p>Haemosporidian parasites are widely recognised as important drivers of avian physiology, with potential effects on oxygen transport and energy balance. These parasites infect red blood cells and consume host haemoglobin, reducing oxygen-carrying capacity. At higher elevations, birds face reduced oxygen availability and are expected to increase haemoglobin to offset hypoxia, which may also influence energy allocation and fat reserves. Here, we tested whether haemosporidian infections constrain this response and whether their effects on haemoglobin and fat reserves become more pronounced at higher elevations compared to lower elevations. We quantified infection presence, intensity, haemoglobin concentration, and fat reserves in 926 birds from 135 species sampled along a 1600 m elevational gradient in a subtropical ecosystem. Haemoglobin concentration was lower in infected birds than in uninfected individuals overall. Haemoglobin increased with elevation in uninfected but not infected birds, implying that infection constrains the ability to cope with lower oxygen availability. Among infected individuals, higher parasite intensities were associated with further reductions in haemoglobin at higher elevations. In contrast, fat reserves were unaffected by infection or elevation and varied only with season, being lower during the wet season regardless of infection status. These findings show that haemosporidian infection imposes a baseline constraint on oxygen transport, with additional costs of parasite load emerging under hypoxic conditions. The absence of effects on fat reserves further indicates that the impacts of infection vary by trait and may go undetected if only energy-based measures are used.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2026 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jav.03580","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148373268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}