Background: Among urban stimuli, anthropogenic noise has been identified to be one of the behavioral drivers of species that rely on acoustic signals for communication. Studies have shown both species-specific and assemblage responses to urban noise, ranging from the modulation of their acoustic frequencies and spatiotemporal adjustments to declines in species richness. In this study, we assessed the citywide relationship between two anthropogenic noise variables (noise levels recorded during bird surveys and daily average noise levels) and vegetation cover with bird species richness. Methods: This study was conducted in the city of Xalapa (Mexico) through a 114 citywide point-count survey. We recorded bird communities at each sampling site. We measured noise levels using a sound level meter while performing point-counts. Then, we generated a map of average daily noise of the city using an array of 61 autonomous recording units distributed across the city of Xalapa and calculated daily noise levels for the 114 points. We ran a linear model (LM) to assess potential relationships between both point-count and daily (24 h) noise values and vegetation cover with bird richness. Results: Results from the LM show: (1) a negative relationship between maximum point-count noise and avian species richness, (2) no relationship between 24 h noise and bird species richness, and (3) a positive relationship between vegetation cover and bird species richness. Conclusions: Results provide evidence that decreases in urban bird species richness do not necessarily imply the permanent absence of species, suggesting that birds can temporarily fly away from or avoid sites when noisy, become cryptic while noisy events are occurring, or be undetected due to our inability to record them in the field during noisy events.

Background: Cities differ from non-urban environments by the intensity, scale, and extent of anthropogenic pressures, which can drive the occurrence, physiology, and behavior of the organisms thriving in these settings. Traits as green cover often predict the occurrence patterns of bird species in urban areas. Yet, anthropogenic noise and artificial light at night (ALAN) could also limit the presence and disrupt the behavior of birds. However, there is still a dearth of knowledge about the influence of urbanization through noise and light pollution on nocturnal bird species ecology. In this study, we assessed the role of green cover, noise, and light pollution on the occurrence and vocal activity of the Mottled Owl (Ciccaba virgata) in the city of Xalapa (Mexico).Methods: We obtained soundscape recordings in 61 independent sites scattered across the city of Xalapa using autonomous recording units. We performed a semi-automated acoustic analysis of the recordings, corroborating all Mottled Owl vocalizations. We calculated two measures of anthropogenic noise at each study site: daily noise (during 24 h) and masking noise (mean noise amplitude at night per site that could mask the owl’s vocalizations). We further performed generalized linear models to relate green cover, ALAN, daily noise, and masking noise in relation to the owl’s occurrence (i.e., detected, undetected). We also ran linear models to assess relationships among the beginning and ending of vocal activity with ALAN, and with the anthropogenic and masking noise levels at the moment of which vocalizations were emitted. Finally, we explored variations of the vocal activity of the Mottled Owl measured as vocalization rate across time.Results: The presence of Mottled Owls increased with the size of green cover and decreased with increases in both artificial light at night and noise levels. At the temporal scale, green cover was positively related with the ending of the owl’s vocal activity, while daily noise and ALAN levels were not related to the timing and vocal output (i.e., number of vocalizations). Furthermore, the Mottled Owl showed a marked peak of vocal activity before dawn than after dusk. Although anthropogenic noise levels varied significantly across the assessed time, we did not find an association between high vocal output during time periods with lower noise levels.Conclusions: Spatially, green cover area was positively related with the presence of the Mottled Owl in Xalapa, while high noise and light pollution were related to its absence. At a temporal scale, daily noise and ALAN levels were not related with the timing and vocal output. This suggests that instead of environmental factors, behavioral contexts such as territoriality and mate interactions could drive the vocal activity of the Mottled Owl. Further studies need to incorporate a wider seasonal scale in order to explore the variation of different vocalizations of this species in relation to environmental and biological factors.

Animal communication has long been thought to be subject to pressures and constraints associated with social relationships. However, our understanding of how the nature and quality of social relationships relates to the use and evolution of communication is limited by a lack of directly comparable methods across multiple levels of analysis. Here, we analysed observational data from 111 wild groups belonging to 26 non-human primate species, to test how vocal communication relates to dominance style (the strictness with which a dominance hierarchy is enforced, ranging from ‘despotic’ to ‘tolerant’). At the individual-level, we found that dominant individuals who were more tolerant vocalized at a higher rate than their despotic counterparts. This indicates that tolerance within a relationship may place pressure on the dominant partner to communicate more during social interactions. At the species-level, however, despotic species exhibited a larger repertoire of hierarchy-related vocalizations than their tolerant counterparts. Findings suggest primate signals are used and evolve in tandem with the nature of interactions that characterize individuals' social relationships.