Rindy C. Anderson’s research while affiliated with Florida Atlantic University and other places

Animal populations can exhibit dramatic variation in individual fitness, and microbiota are emerging as a potentially understudied factor influencing host health. Bacterial diversity and community structure of the gut microbiome are associated with many aspects of fitness in animals, but relatively little is known about the generality of these relationships in wild populations and non‐mammalian taxa. We studied the northern cardinal Cardinalis cardinalis , a member of a taxon that is ecologically important but underrepresented in microbiome research: songbirds. To test for relationships between the microbiota and host fitness, we sampled the cloacal microbiomes of wild cardinals and measured body condition index, assessed coloration of sexual ornaments (beak and plumage), and collected blood to estimate the glucocorticoid response to stress. Both alpha and beta bacterial diversity were related to individual variation in body condition and several sexual ornaments, but not glucocorticoid concentrations. Our results from a free‐living songbird population add to a growing body of research linking avian host fitness to internal bacterial community characteristics. This study sets the stage for manipulative experiments to determine how challenges to fitness and microbiomes may upset these relationships.

Many building blocks of human language can be found within the vocal communication systems of other species, most notably songbirds. One of the most prominent of these building blocks is syntax. While studies of syntax are abundant, a lack of consensus on the definition of syntax in non‐human animal communication studies has led to much debate. Consistent and deliberate use of terminology is needed to facilitate understanding across disciplines. In addition, new terminology may better describe syntactic structure found in vocal signals that are devoid of semantic associations, such as birdsong. Here, we propose two terms to describe the types of syntax commonly found in birdsong: sequential syntax and dialectical syntax. Sequential syntax can be defined as the rules that govern the patterns of sound without regard to semantic meaning. Dialectic syntax can be defined as sequential syntax that is distinct among different populations or groups with behavioral significance for those groups. Taken together, these two terms can describe the type of syntax seen in ornamental signals, such as birdsong.

There is growing concern that anthropogenic noise has various deleterious effects on wildlife in urban environments. In humans, it has been suggested that anthropogenic noise exposure during childhood can have long-term effects on cognitive processes in adulthood. Here we tested if urban noise impacts avian cognitive performance by testing adult zebra finches (Taeniopygia guttata) on several cognition tasks in the presence or absence of urban noise playback. We also tested if urban noise impacts growth and cognitive development by testing adult zebra finches on cognition tasks after exposing them to urban noise, pink noise, or no noise during their first 90 days of life. We found that urban noise exposure marginally reduced cognitive performance during tests of a novel motor skill but did not reduce performance during tests of color association learning or spatial memory tasks. We found that urban noise exposure during development marginally affected cognitive performance in adulthood on a color association task. While urban noise exposure during development did not affect adult body size, treated males and females developed less bright bill coloration and redder bills, respectively, than untreated birds. Our results suggest that urban noise exposure may affect morphological traits, such as bill color, that influence social interactions and mate choice. Future studies should examine how noise exposure affects other cognitive behaviors, such as social behavior, and how social behavior in turn might exacerbate or mitigate negative effects of noise.

Bachman's Sparrows (Peucaea aestivalis) have unusually large song repertoires for New World sparrows. Answering questions about their function, evolution, and development requires thorough description of these repertoires in multiple populations. Here, we quantified repertoire size, song type sharing, and sequence sharingspecifically, the sharing of preferred song type transitionsof primary songs within each of 2 populations of Bachman's Sparrows at northeastern and southeastern ends of the species' breeding range. We recorded 20 males in southern North Carolina (NC) and 18 males in eastern Florida (FL). Individual repertoire size had a mean of 4849 song types in both populations. Within each population, males shared many song types, with 80% repertoire overlap between any 2 males in NC and 49% in FL. This within-population song sharing was independent of distance between males' territories. The sequence in which males sang song types was neither stereotyped nor random, and within each population, preferred song transitions were shared by all (NC) or most (FL) pairs of males. The sharing of preferred song transitions was also not correlated with the distance between territories, suggesting that birds do not adjust repertoires or song sequences in adulthood to match more closely those of territory neighbors. The function and ontogeny of the repertoire features documented here in Bachman's Sparrowslarge repertoires with high sharing of both song types and preferred song transitionsinvite further study. Los gorriones Peucaea aestivalis tienen repertorios de canto inusualmente grandes entre los gorriones del Nuevo Mundo. La respuesta a preguntas sobre su funcin, evolucin y desarrollo requiere descripciones completas de dichos repertorios en mltiples poblaciones. Aqu cuantificamos el tamao del repertorio, intercambio de tipos de canto y secuencias en especfico, el intercambio de transiciones de tipos de canto preferidas de cantos primarios al interior de 2 poblaciones de este gorrin en los extremos noreste y sureste del rango reproductivo de esta especie. Grabamos 20 machos en North Carolina (NC) y 18 machos en el este de Florida (FL). El tamao promedio del repertorio fue de 4849 tipos de canto en ambas poblaciones. Dentro de cada poblacin, los machos compartieron muchos tipos de canto, con 80% de traslape de repertorios en cualquiera de 2 machos en NC y 49% en FL. Estos cantos compartidos al interior de la poblacin fue independiente de la distancia entre territorios de los machos. La secuencia en la que los machos cantaron los diferentes tipos de canto no fue estereotipado o aleatorio, y al interior de cada poblacin, las transiciones preferidas de canto fueron compartidas por todos (NC) o la mayora (FL) de los pares de machos. Las transiciones de cantos preferidas tampoco estuvieron correlacionadas con la distancia entre territorios, lo que sugiere que las aves no ajustan sus repertorios o secuencias de canto en la edad adulta para concordar ms cercanamente con las de sus vecinos de territorio. La funcin y ontogenia de las caractersticas del repertorio de este gorrin que documentamos aqu repertorios grandes con gran parte de cantos compartidos de tipos de canto y transiciones de cantos preferidas nos invitan a realizar ms estudios. Palabras clave: bioacstica, canto de aves, Passerellidae, secuencias vocales, variacin especial.

Many wild populations of animals conform to the ideal despotic distribution (IDD) in which more competitive individuals exclude less competitive individuals from high quality resources. Body size and aggressiveness are two important traits for resource defense, and they positively covary so that larger individuals are usually more aggressive. Using Bachman’s sparrows, we tested the hypothesis that larger birds are more aggressive and are thus able to compete for the best quality territories. We found that larger males were more aggressive, and more aggressive birds fledged at least one young. However, we did not find consistent relationships between aggressiveness and habitat characteristics. Our results suggest that Bachman’s sparrows meet most of the predictions of the IDD. Frequent ecological disturbances, such as fires, might disrupt the IDD or make it difficult to detect. Additional studies are needed to test for relationships between ecological disturbances and territorial behaviour.

In territorial species, nonterritorial floaters may be critical to population dynamics. One theoretical framework, based on the assumption that floating is a strategic decision to forego reproduction, predicts that selection maintains an abundant floater population even if low‐quality territories are available. However, existing models make two critical assumptions: all individuals have equal competitive ability, and every individual in a population has access to every available territory. We assess the consequences of relaxing these assumptions in a model of asymmetric competition with a trade‐off between investment in competitiveness and reproductive success. Our results demonstrate that selection for greater competitiveness eliminates floater production unless the outcome of territorial contests has a strong stochastic component. Next, we suppose individuals can compete for territories only within a fixed neighborhood. If this constraint is sufficiently strong, our model predicts that a population will produce floaters. Finally, we show that our model makes novel predictions regarding the maintenance of trait variation and the relationship between this variation and the distribution of competitors among unequal territories.

Recent research in mammals supports a link between cognitive ability and the gut microbiome, but little is known about this relationship in other taxa. In a captive population of 38 zebra finches (Taeniopygia guttata), we quantified performance on cognitive tasks measuring learning and memory. We sampled the gut microbiome via cloacal swab and quantified bacterial alpha and beta diversity. Performance on cognitive tasks related to beta diversity but not alpha diversity. We then identified differentially abundant genera influential in the beta diversity differences among cognitive performance categories. Though correlational, this study provides some of the first evidence of an avian microbiota–gut–brain axis, building foundations for future microbiome research in wild populations and during host development.