In the company of cowbirds, Molothrus ater ater: robust patterns of sociability predict reproductive performance.

Many species exhibit behavioral tendencies that are stable over time and across contexts. Robust variation in sociability, or the propensity to approach others, is widespread across the vertebrates. Nonetheless, the influence of sociability on reproductive performance is largely unknown. In this study, we explore the relationship between sociability and reproductive behavior in flocks of Brown-headed Cowbirds (Molothrus ater ater). In spring 2011, we separated birds into three large aviaries based on the number of approaches they initiated and received during fall 2010. Females were separated into high, intermediate, and low sociable flocks, while male sociability was spread evenly across the three flocks. Here we report for the first time that different patterns of social approach tendencies in the fall predicted reproductive behavior in the spring. The high sociable flocks contained more laying females who produced more eggs in contrast to the other flocks. Male courtship behavior was comparable across the three flocks. These findings suggest that robust variation in sociability is an important factor in reproductive performance.

Different patterns of contingent stimulation differentially affect attention span in prelinguistic infants.

The ability to sustain attention influences different domains including cognitive, motor, and communicative behavior. Previous research has demonstrated how an infant's parent can influence sustained attention. The purpose of our study was to expose infants systematically to both sensitive and redirective patterns of behavior to examine how unfamiliar individuals could influence attention. Results revealed infants changed their patterns of looking with the unfamiliar individuals. Infants had longer durations of sustained attention when interacting with a sensitive unfamiliar individual who followed into their attentional focus as opposed to an intrusive person who led their attentional focus. This study demonstrates that infants discriminate patterns of contingency to persons seen for only a short period of time broadening the range of potential mentors for learning.

Behavioral compatibility and reproductive outcomes in two distant populations of captive brown-headed cowbirds (Molothrus ater).

Increased understanding of geographic variation in courtship behavior in animal species can provide insight into the ways behavior may influence evolutionary change. Here, the relationship of geographic variation in courtship behavior to reproductive outcomes was tested in two distant and behaviorally distinct populations of brown-headed cowbirds, Molothrus ater, by comparing rates of copulation and egg production. Females from an Indiana (IN) population and a South Dakota (SD) population were housed in aviaries with males from either their own population (INsame and SDsame) or the other population (INmix and SDmix). Over the breeding season, INsame females exhibited higher rates of copulation and egg production compared with INmix females, but no differences were detected between SDsame and SDmix females. The data suggest that behavioral differences between IN and SD cowbirds are the likely cause of lower egg production in the INmix females.

Constructing culture in cowbirds (Molothrus ater).

In past work, the authors produced divergent patterns of courtship and communication in juvenile male cowbirds (Molothrus ater) by providing them with different social experiences during their 1st year. Here the authors determined whether these different social patterns could be transmitted to new generations of juvenile males. In Experiment 1, the authors exposed groups of juveniles to adult males who differed in the amount of male-male competition they produced. In Experiment 2, they gave groups of juveniles either social access to adult males or only visual and acoustic access to those males. In both experiments, juvenile males developed patterns of courtship and competition similar to those expressed by the adult males with whom they had social contact. The juveniles never had the opportunity to observe some of the adults' behaviors that they came to replicate. This suggests that the role of the adults was to establish the social structure in the groups, modifying juveniles' early social interactions. Juveniles were then "cultured" within these different learning environments, constructing social behavior similar to the adult males' behavior in their 1st year.

Developmental origins of sociality in brown-headed cowbirds (Molothrus ater).

Five variables were studied relating to the emergence of sociality in hand-reared cowbirds (Molothrus ater): proximity, sex assortment, reactions to adults, head-down displays, and vocalizations. The authors were especially interested in female sociality because adult female birds influence male courtship, song content, and use through proximity, attention, and displays. The authors found that young female birds failed to show same-sex affiliation typical of the species at any point in the study. Brief introduction of adults did not affect social patterns. Adults used more head-down displays than juveniles, who used more displays with familiar peers. Directed and undirected singing emerged concurrently; directed singing was positively correlated with earlier hatching. This is the first demonstration of the need for early learning in the development of female sociality.

Social interaction shapes babbling: testing parallels between birdsong and speech.

Birdsong is considered a model of human speech development at behavioral and neural levels. Few direct tests of the proposed analogs exist, however. Here we test a mechanism of phonological development in human infants that is based on social shaping, a selective learning process first documented in songbirds. By manipulating mothers' reactions to their 8-month-old infants' vocalizations, we demonstrate that phonological features of babbling are sensitive to nonimitative social stimulation. Contingent, but not noncontingent, maternal behavior facilitates more complex and mature vocal behavior. Changes in vocalizations persist after the manipulation. The data show that human infants use social feedback, facilitating immediate transitions in vocal behavior. Social interaction creates rapid shifts to developmentally more advanced sounds. These transitions mirror the normal development of speech, supporting the predictions of the avian social shaping model. These data provide strong support for a parallel in function between vocal precursors of songbirds and infants. Because imitation is usually considered the mechanism for vocal learning in both taxa, the findings introduce social shaping as a general process underlying the development of speech and song.

The presumption of sociality: social learning in diverse contexts in brown-headed cowbirds (Molothrus ater).

Data are presented on social and vocal learning in cowbirds (Molothrus ater) housed in large aviaries and given more degrees of freedom than in conventional experimental studies. The studies show that social and vocal outcomes are facultative responses to social contexts. Several findings are reviewed: First, cowbirds quickly self-organize into groups by age and sex; second, opportunities to interact across age and sex do exist and affect courtship competence; third, female cowbirds organize themselves differently in the presence and absence of male competition; and fourth, young, naive cowbirds show rapid and differential sensitivity to group dynamics. Taken as a whole, the data show that social Umwelten are dynamic, developmental ecologies.