Journal of Avian Biology最新文献

{"title":"Weak population structure in the North American house wren Troglodytes aedon","authors":"William C. Anderson,&nbsp;Erik R. Funk,&nbsp;Angela N. Theodosopoulos,&nbsp;Kathryn C. Grabenstein,&nbsp;Garth Spellman,&nbsp;Scott A. Taylor","doi":"10.1111/jav.03401","DOIUrl":"https://doi.org/10.1111/jav.03401","url":null,"abstract":"<p>Cryptic genetic differentiation is being increasingly documented in birds and other organisms using genome-wide variation. A recent example of cryptic genetic differentiation in a widespread species with conserved morphology is the northern house wren <i>Troglodytes aedon</i>. We found that, despite extremely similar morphology and no documented vocal differences, the two subspecies of the northern house wren, <i>T. a. aedon</i> (eastern) and <i>T. a. parkmanii</i> (western), exhibited both nuclear and mitochondrial genomic differentiation. Individuals present along the Front Range of the Colorado Rocky Mountains possessed nuclear genetic variation intermediate between <i>T. a. aedon</i> and <i>T. a. parkmanii</i>; additionally, both divergent mitochondrial lineages, corresponding to the western and eastern northern house wren populations, occur in Colorado. However, the dynamics of this putative contact zone (i.e. amount of hybridization or introgression) and the degree of differentiation between the two subspecies remain uncharacterized. To expand our understanding of northern house wren population genetic differentiation and explore the possibility of hybridization, we used a double digest restriction-site associated (ddRAD) approach and sequenced 127 northern house wrens, including 109 individuals from across Colorado and Wyoming, as well as nine individuals each from eastern and western allopatric regions. Our results highlight that <i>T. a. aedon</i> occur significantly further west than previously thought, and provide evidence for weak population structure within the northern house wren, while generally setting the stage for future investigations of northern house wren population genomics and the genetic basis of cryptic speciation.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2025 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03401","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143248632","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":"Serenade of a whimbrel: understanding the function of display behaviour in a sub-Arctic territorial wader","authors":"Maite Cerezo-Araujo,&nbsp;José Augusto Alves,&nbsp;Gunnar Thor Hallgrimsson,&nbsp;Bodvar Thórisson,&nbsp;Tómas Grétar Gunnarsson,&nbsp;Verónica Méndez","doi":"10.1111/jav.03324","DOIUrl":"https://doi.org/10.1111/jav.03324","url":null,"abstract":"<p>Animal sounds contain important information used in intra- and inter-species communication. For species exhibiting elaborate and energetically expensive signals such as aerial displays accompanied by a call, the nature of the message being transmitted is honest and usually reflects individual fitness. Display events that combine flight and calls and are executed during the breeding season have traditionally been associated with two main functions: repelling rivals and/or attracting mates. In waders, the distinction between the two may rely on the timing of the breeding season at which displays occur, but also on the frequency at which displays occur in relation to local breeding density. Here, we investigated the function of display behaviour in the Icelandic whimbrel throughout the breeding season and along a breeding density gradient. We used a site-based approach in the southern lowland plain in Iceland where whimbrel breeding density and display frequency were recorded for two years. Although whimbrels showed display behaviour throughout the entire season, display frequency was higher at low densities during pre-incubation but similar at different densities during incubation and post-incubation. Our results indicate that this behaviour is context-dependent and multi-functional, supporting the importance of mate attraction at low conspecific density during pre-incubation, while other functions such as resource defence may be important throughout the breeding season.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2025 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03324","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143248634","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":"Circulating miRNAome of avian influenza-infected ruddy turnstones Arenaria interpres","authors":"Anne-Fleur Brand,&nbsp;Courtney A. Waugh,&nbsp;Jorge M. O. Fernandes,&nbsp;Marcel Klaassen,&nbsp;Michelle Wille,&nbsp;Veerle L. B. Jaspers,&nbsp;Rune Andreassen","doi":"10.1111/jav.03404","DOIUrl":"https://doi.org/10.1111/jav.03404","url":null,"abstract":"<p>MicroRNAs (miRNAs) are highly conserved small noncoding RNAs that regulate gene expression post-transcriptionally. Circulating miRNAs – miRNAs that have been released from cells and circulate in the bloodstream – are relatively stable and interesting molecules for wildlife research, where they may form a proxy for gene expression as a function of the animal's state under a variety of environmental challenges. Aiming at providing initial baseline data on the circulating miRNAome in avian wildlife, we assessed the miRNA profiles of wild ruddy turnstones <i>Arenaria interpres</i> on their Australian non-breeding grounds. The ruddy turnstone is a long-distant migrant and a significant reservoir species for low pathogenic avian influenza virus (LPAIV). We therefore investigated both LPAIV-infected and uninfected individuals for their specific miRNA profiles to potentially elucidate the species' molecular mechanisms underlying its response to LPAIV infection. <i>De novo</i> miRNA characterisation in the ruddy turnstone genome identified 161 conserved and two novel, bird-specific miRNAs, with liver-enriched miRNA-122 being the most abundant. Z chromosome-linked miR-2954-3p was significantly more abundant in serum from males (ZZ) than from females (ZW). Furthermore, we found a sex- and age-associated effect of LPAIV infection on miRNA abundance in serum samples, including one novel miRNA. This circulating miRNA signature may reflect sex- and age-specific differences in the host response, indicating that circulating miRNAs could serve as a valuable non-destructive analytical tool for enhancing our understanding of avian infections in a wildlife context and should be explored further.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2025 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03404","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143248635","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":"Assessing the impacts of livestock grazing on upland bird breeding territories using drone surveys","authors":"Robin J. Pakeman,&nbsp;Damian Bienkowski,&nbsp;Debbie A. Fielding,&nbsp;Andre Thiel,&nbsp;Darren M. Evans","doi":"10.1111/jav.03356","DOIUrl":"https://doi.org/10.1111/jav.03356","url":null,"abstract":"<p>Ground nesting birds are sensitive to habitat structure, so understanding this relationship is fundamental to managing habitat to maintain or enhance bird populations. We used an existing long-term, large-scale experiment with routine monitoring of meadow pipit territories to assess the capability of drone-based remote sensing as a means of capturing relevant habitat information. Normalised Difference Vegetation Index (NDVI) captured differences in stocking density between treatments, and autumn-measured NDVI was well correlated to field measurements of vegetation height and density. Spring and autumn NDVI were negatively correlated due to dominant tussock-forming species dying back over winter. Meadow pipit apparent territory size was positively correlated to autumn NDVI and to the difference between autumn and spring NDVI. Apparent territory size was larger where there was more tussocky vegetation that comprise the areas least preferred for foraging. The long-lived nature of tussocks likely constrains the effect of the grazing treatments on meadow pipit breeding apparent territory size. Drone-based remote sensing of habitat characteristics appears to be a powerful way forward to understand bird–habitat associations.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2025 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03356","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143248477","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":"Genetic analysis of museum samples suggests temporal stability in the Mexican nonbreeding distribution of a neotropical migrant","authors":"Sheela P. Turbek,&nbsp;Alexandria Polich,&nbsp;Christen M. Bossu,&nbsp;Christine Rayne,&nbsp;Amanda Carpenter,&nbsp;Genaro Rodríguez Otero,&nbsp;Sergio Gómez Villaverde,&nbsp;Fabiola Rodríguez Vásquez,&nbsp;Blanca E. Hernández-Baños,&nbsp;John McCormack,&nbsp;Kristen Ruegg","doi":"10.1111/jav.03369","DOIUrl":"https://doi.org/10.1111/jav.03369","url":null,"abstract":"<p>Seasonal migration is highly labile from an evolutionary perspective and known to rapidly evolve in response to selective pressures. However, long-distance migratory birds rely partially on innate genetic programs and may be constrained in their ability to alter their migratory behavior. We take advantage of recent advances in our ability to genotype historical DNA samples to examine the temporal stability of migratory connections between breeding and nonbreeding populations (i.e. migratory connectivity) and population-level nonbreeding distributions in the Wilson's warbler <i>Cardellina pusilla</i>, a long-distance migratory songbird. By assigning historical and contemporary samples collected across the nonbreeding range to genetically distinct breeding clusters, we suggest that broad-scale population-level nonbreeding distributions within this species have remained largely consistent within Mexico from the mid-1900s to the present day. These findings support the idea that the nonbreeding distributions of long-distance migrants may remain stable over long time scales, even in the face of rapid environmental change.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2025 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03369","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143248633","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":"Effects of immune status on stopover departure decisions are subordinate to those of condition, cloud cover and tailwind in autumn-migrating common blackbirds Turdus merula","authors":"Tjomme van Mastrigt,&nbsp;Kevin D. Matson,&nbsp;Sander Lagerveld,&nbsp;Xinrou S. Huang,&nbsp;Willem F. de Boer,&nbsp;Henk P. van der Jeugd","doi":"10.1111/jav.03368","DOIUrl":"https://doi.org/10.1111/jav.03368","url":null,"abstract":"<p>Migratory birds encounter a large variety of parasites and pathogens en route and invest in immune defences to limit the risk and fitness costs of infection. Since both migration and immune defences carry costs, individuals on tight budgets may face trade-offs between migratory progress and immune status. Many species alternate legs of strenuous migratory flight with stopovers during which birds refuel, rest, and recover physiologically. Despite this, most time and energy consumed during migration are actually spent on stopovers. As a result, identifying what determines stopover duration is key in understanding how migratory birds balance investments in immune defences and migration. Yet, it is unknown under what conditions an individual's immune status may affect migratory progress through the duration of stopovers. We explored whether immune status at arrival affects stopover duration by radio-tagging and blood-sampling common blackbirds <i>Turdus merula</i> during autumn stopovers on the Dutch island of Vlieland. To measure immune status, we quantified levels of bacterial killing ability, natural antibodies, complement, and haptoglobin, as well as heterophil–lymphocyte ratios. We show that stopover departures peaked during periods with low cloud cover and strong tailwinds. While lean birds prolonged stopovers, we only found a weak tendency of prolongation in birds with elevated haptoglobin levels. We conclude that effects of immune status on minimum stopover durations are subordinate to those of condition, cloud cover, and tailwinds in autumn-migrating common blackbirds. Hence, future studies on the link between immune defences and stopover durations should take weather conditions into account.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2025 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03368","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143595431","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":"Factors influencing nest site selection in a rapidly declining shorebird, the Eurasian curlew","authors":"Eleanor Marie Rivers,&nbsp;Mike J. Short,&nbsp;Andy Page,&nbsp;Peter M. Potts,&nbsp;Kathy Hodder,&nbsp;Andrew Hoodless,&nbsp;Rob Robinson,&nbsp;Richard Stillman","doi":"10.1111/jav.03286","DOIUrl":"https://doi.org/10.1111/jav.03286","url":null,"abstract":"<p>In this period of rapid human-induced environmental change, it is vital that influences of habitat on the distribution and productivity of threatened species are understood. Ground-nesting birds are declining more rapidly across Europe than any other group, with large-bodied birds at the greatest risk of extinction. Productivity and adult survival cannot both be maximised concurrently, and individuals will make decisions during the nest-placement phase which will favour one outcome or the other; however, under conditions of accelerating change, these decision processes may become decoupled from positive fitness outcomes. The Eurasian curlew <i>Numenius arquata</i> is Europe's largest wader and is showing steep declines in breeding productivity. Curlews are known to use a diverse range of habitats for nesting, where anthropogenic or natural features may influence distribution. There is an urgent need to understand the spatial scales of these impacts, and whether habitat characteristics have a positive or negative impact on nest survival. In our study site in southern England, curlew showed a marked preference for nesting in wetter habitats, primarily mire, and a weaker selection of dry heathland. Nest survival improved in wetter habitats, and the area of mire round a nest site was positively associated with increased levels of nesting success, whilst area of scrub had a negative association. Woodland significantly excluded curlew from potentially suitable breeding habitat, with an impact observed up to 2 km from the nest site, but nest survival did not improve with distance from woodland. Curlews strongly avoided nesting near a major road passing through the study site, despite seemingly suitable habitat nearby. Understanding landscape effects will assist in planning future habitat management for curlew, impacts of forestry and avoidance of additional pressures on a species of high conservation concern.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2025 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03286","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143252535","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":"Comparative analysis of the plasma metabolome of migrating passerines: novel insights into stopover metabolism","authors":"Adi Domer,&nbsp;Weronika Jasinska,&nbsp;Leah Rosental,&nbsp;Eyal Shochat,&nbsp;Saleh Alseekh,&nbsp;Alisdair R. Fernie,&nbsp;Yariv Brotman,&nbsp;Ofer Ovadia","doi":"10.1111/jav.03331","DOIUrl":"https://doi.org/10.1111/jav.03331","url":null,"abstract":"<p>During long-distance migration, many birds experience periods of either prolonged fasting (during endurance flights) or extensive feeding (during stopovers). Despite decades of research on avian metabolism during migration, many questions have remained unanswered, as such research mainly focused on targeted metabolites and fat metabolism. Here, we examined the plasma-metabolome of two migrating passerine species before they crossed the Sahara Desert. Birds were sampled at two sites populated by Pistacia trees bearing fat-rich fruits and at an additional site dominated by blooming Eucalyptus trees. The blood samples were analyzed using both GC-MS and LC-MS, using an untargeted approach. Examination of metabolic pathways activated during stopovers indicated a crucial role for cycling glucose through the Cori and Cahill cycles in resting and recovery processes. This novel perspective, conducted on free-ranging birds, suggests the evolution of avian insulin resistance due to factors such as endurance exercise, fasting, and a preference for fatty acid oxidation during migration, akin to cell trauma recovery. We detected significant inter-site variations in birds' polar and lipophilic metabolic profiles. We interpret the differences in the polar metabolites to be associated with the physiological state of the birds, with birds that are considered to have landed during the night prior to capture showing different metabolic profiles compared to birds that have spent more time at the stopover site. In contrast, distinctions in the lipophilic profiles of birds were associated with variations in the primary food source that was available to them in the different sites. This study underscores the challenge of interpreting commonly used indicators for assessing migrating birds' physiological state, which was predominantly derived from lipid metabolism in complex ecological systems.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2025 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03331","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143595081","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":"Introducing the mini-review article category and the Journal of Avian Biology review award","authors":"Michael Tobler,&nbsp;Theresa Burg,&nbsp;Dominique Potvin,&nbsp;Jan-Åke Nilsson","doi":"10.1111/jav.03423","DOIUrl":"https://doi.org/10.1111/jav.03423","url":null,"abstract":"&lt;p&gt;Journal of Avian Biology (JAB) publishes hypothesis-driven, high-quality research from all parts of the globe that advances our understanding of the ecology, evolution and behaviour of birds. Findings can be disseminated in research articles, short communications, viewpoint articles and reviews. Reviews perform an important function as vehicles to convey critical information in a synthesized way; they not only aggregate information, but also identify current research gaps and pave the way for future investigation. Comprehensive review articles, however, are major undertakings that may quickly go out of date. To address this challenge and to offer a nimbler format to publish overviews of a particular field or aspect in avian biology, JAB introduced the ‘mini-review' article category in December 2022. As the name suggests, mini-reviews are shorter than standard reviews (about 6000 words) and can be used to highlight a sub-topic or ongoing debate within a broader research area. They provide a succinct and clear summary of the research topic and give readers a quick overview of the most recent and significant advances.&lt;/p&gt;&lt;p&gt;Journal of Avian Biology is an important outlet for young researchers. Of all the articles published in 2023, nearly 60% had a corresponding author with no more than 8 years of post-doctorate research experience. Most of the corresponding authors on these papers (close to 50%) were PhD students or early postdocs at the time of publication. To emphasize this and to highlight the mini-review category as a new outlet for early career researchers to synthesize their research, JAB announced the first ‘JAB review award' competition in spring 2023. The award is sponsored by the Nordic Society Oikos (NSO), the umbrella society for the ecological societies in the Nordic countries, who publishes JAB and four other scientific journals (Oikos, Nordic Journal of Botany, Ecography and Wildlife Biology).&lt;/p&gt;&lt;p&gt;The JAB review award is given to an early career research scientist who has an exceptional mini-review manuscript accepted for publication in JAB. The mini-review should focus on new developments and/or emerging concepts in the areas of avian research that fall within the scope of the journal. The winner of the JAB review award receives a 1000€ honorarium and the runner-up receives 500€. If the award is given for a paper with multiple authors (the lead and corresponding author(s) must be early career), those meeting the early career research criteria at the time of publication will share the monetary prize. All accepted papers that are entered in the competition will appear together in an issue in Journal of Avian Biology.&lt;/p&gt;&lt;p&gt;In this first ‘award issue', we briefly reiterate eligibility and submission criteria, and outline the assessment criteria for the award. We wish to be clear and transparent about these criteria as it recently has been highlighted that there is not enough transparency in scientific awards for early- and mid-car","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2024 11-12","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03423","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664799","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 interplay of resource availability and parent foraging strategies on juvenile sparrow individual specialization","authors":"Natalia Ricote,&nbsp;Constanza Weinberger,&nbsp;Natalia Ramírez-Otarola,&nbsp;Sara Bustamante,&nbsp;María Lucía Málaga,&nbsp;Gonzalo Barceló,&nbsp;Pablo Sabat,&nbsp;Seth D. Newsome,&nbsp;Karin Maldonado","doi":"10.1111/jav.03391","DOIUrl":"https://doi.org/10.1111/jav.03391","url":null,"abstract":"<p>Temporal variation in resource availability, amplified by global change, may have strong impacts on species breeding at temperate and high latitudes that cue their reproduction to exploit seasonal resource pulses. This study examines how resource availability and parental care influence niche partitioning between and within age classes in the rufous-collared sparrow, which provides extensive parental care. We hypothesized juveniles would exhibit narrower niches focused on high-quality resources compared to adults, regardless of resource availability. We used stable isotope analysis to quantify individual and population niches in juveniles and adults across the breeding season in two cohorts experiencing contrasting resource landscapes. Contrary to our initial hypothesis, juveniles exhibited greater among-individual diet variation and smaller total niche widths (i.e. higher levels of individual specialization, IS) during periods of high food availability in comparison to periods of food scarcity. Interestingly, total niche width and IS of adults remained stable across seasons despite a shift in trophic level, highlighting their potential role in providing a consistent diet for their young. These findings reveal a dynamic interplay between resource availability, parental care, and IS, with important implications for understanding population resilience under variable resource scenarios. The study also suggests that adult sparrows modify their provisioning strategies based on resources, potentially buffering offspring from environmental fluctuations. Understanding age-specific responses to resource variation is crucial for predicting species responses to ecological conditions, particularly in regions like central Chile where seasonal resource limitation is expected to become more variable in response to climate change.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":"2025 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03391","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143595711","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}