Phenotype networks reveal differences between practice and courtship displays in swallow-tailed manakins

Understanding complex multimodal courtship displays in terms of the integrational properties of sexual traits, their functions and how they change in different contexts is a challenge in behavioural ecology, since sexual behaviours can present a diverse set of evolutionary implications. Here, we used phenotype networks to evaluate displays of the swallow-tailed manakin, Chiroxiphia caudata (Passeriformes: Pipridae) in two social contexts: (1) practice displays and (2) courtship displays. We built three-modality and two-modality phenotype networks using sound, motor and colour traits extracted from audio and video recordings and plumage. We hypothesized that networks in both contexts would be modular, as a consequence of a higher degeneracy within than between traits in each modality, as traits are produced by different physiological mechanisms. We collected data from a population in an Atlantic Forest remnant in southern Brazil during three breeding seasons (October–March 2015–2018). We found that practice networks had higher modularity than courtship networks, which was the opposite of what we expected. The constrained patterns of practice networks suggest that juvenile males perform a strict stereotypical display due to developmental constraints, while the higher variability between traits for adult males may indicate their capability of adjusting performances depending on female responses and preferences. Our study sheds light on how different social contexts can alter the relation between traits and also provides future directions for what traits should be explored to unravel this complex display function.