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Environmental stress, especially during development, can cause important phenotypic changes in individuals. In songbirds, these stress-induced changes have been shown to include impaired learning of song and reduced song complexity in several species. Typically, developmental stress has been studied in terms of individual variation within a population; however, birdsong, a culturally transmitted trait, may undergo relatively rapid changes if widespread learning impairment results from population-level environmental stress, and these changes could potentially be amplified if affected individuals become the song tutors for future generations. We thus hypothesize that ecosystem-wide stressors may cause population-level changes to birdsong. Here, we use publicly available birdsong recordings to determine whether song differences were evident after an abnormal and severe 2016 drought in western New York State. We analyzed birdsong recordings of two species, the Dark-eyed Junco (Junco hyemalis) and the Song Sparrow (Melospiza melodia), recorded between 2006–2020 in the drought-affected region and, for comparison, in two nearby regions less affected by the drought. The population-level song features of the species with more complex songs (Song Sparrow) changed in the drought area after 2016, but not in the control area. In the species with a more simple song (Dark-eyed Junco), we detected song changes in both regions, suggesting that the drought did not have an outsized effect on song in this species. These findings support a more nuanced hypothesis that stress-induced deficits may disproportionately affect species with songs that are more difficult to learn. These conclusions are tempered by the relatively sparse recording availability from years prior to 2016, but we predict that future longitudinal studies of song evolution in natural populations will be more tractable given the nearly exponential increase in the number of song recordings deposited in public repositories in recent years, making this experimental design a useful framework for future studies. 

The transition to specialization of knowledge within populations could have facilitated the accumulation of cultural complexity in humans. Specialization allows populations to increase their cultural repertoire without requiring that members of that population increase their individual capacity to accumulate knowledge. However, specialization also means that domain-specific knowledge can be concentrated in small subsets of the population, making it more susceptible to loss. Here, we use a model of cultural evolution to demonstrate that specialized populations can be more sensitive to stochastic loss of knowledge than populations without subdivision of knowledge, and that demographic and environmental changes have an amplified effect on populations with knowledge specialization. Finally, we suggest that specialization can be a double-edged sword; specialized populations may have an advantage in accumulating cultural traits but may also be less likely to expand and establish themselves successfully in new demes owing to the increased cultural loss that they experience during the population bottlenecks that often characterize such expansions. This article is part of the theme issue ‘Human socio-cultural evolution in light of evolutionary transitions’. 

Four zebra finches in a closed research colony presented with variable clinical signs, including masses, skin lesions,shivering, and/or ruffled feathers. These birds were not responsive to treatment efforts; 3 died and one was euthanized. All4 were submitted for necropsy to determine the cause of the clinical signs. Gross necropsy and histopathologic findings fromall birds resulted in a diagnosis of round cell neoplasia in multiple organs, including the skin, liver, kidney, and reproductivetract, with intranuclear inclusion bodies in the neoplastic cells. In all 4 cases, immunohistochemical staining showed strongimmunoreactivity for CD3 in 70% to 80% of the neoplastic round cells, with a relatively small subset that were immunopositivefor Pax5. These findings supported a diagnosis of T-cell lymphoma. Frozen liver tissue from one case was submittedfor next-generation sequencing (NGS), which revealed viral RNA with 100% sequence homology to canary polyomavirusstrain 34639 that had originally been identified in a European goldfinch. Formalin-fixed paraffin-embedded scrolls fromanother case were also submitted for NGS, which revealed viral RNA with 97.2% sequence homology to canary polyomavirusstrain 37273 that had originally been identified in a canary. To localize the virus in situ, RNAscope hybridizationwas performed using a probe designed to target the VP1 gene of the sequenced virus in frozen liver tissue. In all 4 cases,disseminated and robust hybridization signals were detected in neoplastic cells. These findings indicate that polyomaviruseshave the potential to be oncogenic in zebra finches. 

The development of rhythmicity is foundational to communicative and social behaviours in humans and many other species, and mechanisms of synchrony could be conserved across species. The goal of the current paper is to explore evolutionary hypotheses linking vocal learning and beat synchronization through genomic approaches, testing the prediction that genetic underpinnings of birdsong also contribute to the aetiology of human interactions with musical beat structure. We combined state-of-the-art-genomic datasets that account for underlying polygenicity of these traits: birdsong genome-wide transcriptomics linked to singing in zebra finches, and a human genome-wide association study of beat synchronization. Results of competitive gene set analysis revealed that the genetic architecture of human beat synchronization is significantly enriched for birdsong genes expressed in songbird Area X (a key nucleus for vocal learning, and homologous to human basal ganglia). These findings complement ethological and neural evidence of the relationship between vocal learning and beat synchronization, supporting a framework of some degree of common genomic substrates underlying rhythm-related behaviours in two clades, humans and songbirds (the largest evolutionary radiation of vocal learners). Future cross-species approaches investigating the genetic underpinnings of beat synchronization in a broad evolutionary context are discussed. This article is part of the theme issue ‘Synchrony and rhythm interaction: from the brain to behavioural ecology’.