Las bandadas mixtas (BM) son asociaciones de diferentes especies que se forman como estrategia para aumentar la eficiencia de forrajeo y/o reducir el riesgo de predación. El objetivo del presente trabajo fue determinar la variación en la composición y estructura de las BM, a lo largo del gradiente latitudinal de la selva montana de las Yungas argentinas. Ocho sitios fueron estudiados a lo largo de los 700 km de distribución de las Yungas en el país. En cada sitio se establecieron 10 transectas visitadas de junio a septiembre entre 2006 y 2009. Se determinó riqueza y abundancia de las BM. Se observaron 325 BM, con un total de 72 especies participantes y una abundancia de 2480 individuos. Diecisiete familias estuvieron representadas, 15 del Orden Passeriformes y 2 no-Passeriformes (Trochilidae y Picidae). Las familias más importantes fueron Tyrannidae (12 especies), Furnariidae (10 especies) y Thraupidae (nueve especies). Doce especies fueron omnipresentes en los ocho sitios de estudio y las especies que tuvieron los valores de ocurrencia más altos fueron: Syndactyla rufosuperciliata, Phylloscartes ventralis, Chlorospingus flavopectus y Myioborus brunniceps. Aunque los análisis estadísticos multivariados indicaron que el gradiente latitudinal no tendría influencia directa sobre las características estructurales (número de bandadas, número de especies e individuos involucrados) de las BM, la composición de especies varió en asociación con la latitud. Algunas causas asociadas al gradiente, como el clima local, características de la vegetación y disponibilidad de alimento, podrían influir en los resultados obtenidos.

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The literature on mixed-species flocks references a wide variety of bird associations. These studies, however, have used an array of unstructured characteristics to describe flocks, ranging from the temporal occurrence of flocking to the identity and behavioural features of constituent members, with little consensus on which key traits define and characterize a mixed-species flock. Moreover, although most studies report species-specific roles, there is no clear consensus about what these roles signify nor how to define them. This lack of consistency limits our ability to compare flocks from different habitats, regions and species pools. To unify this sizable body of literature, we reviewed and synthesized 538 studies on mixed-species flocks. We propose 13 categories to classify mixed-species flocks using behavioural and physical traits at the flock and participant level, as well as the habitat where the flock occurs. Lastly, we discuss the historical terminology for different species roles and propose definitions to clarify and distinguish among nuclear, leader, sentinel, and flock-following species. We envision that these guidelines will provide a universal language for mixed-species flock research, paving the way for future comparisons and new insight between different regions and systems. This article is part of the theme issue ‘Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes’.

Birds in mixed-species flocks benefit from greater foraging efficiency and reduced predation, but also face costs related to competition and activity matching. Because this cost–benefit trade-off is context-dependent (e.g. abiotic conditions and habitat quality), the structure of flocks is expected to vary along elevational, latitudinal and disturbance gradients. Specifically, we predicted that the connectivity and cohesion of flocking networks would (i) decline towards tropical latitudes and lower elevations, where competition and activity matching costs are higher, and (ii) increase with lower forest cover and greater human disturbance. We analysed the structure of 84 flock networks across the Andes and assessed the effect of elevation, latitude, forest cover and human disturbance on network characteristics. We found that Andean flocks are overall open-membership systems (unstructured), though the extent of network structure varied across gradients. Elevation was the main predictor of structure, with more connected and less modular flocks upslope. As expected, flocks in areas with higher forest cover were less cohesive, with better defined flock subtypes. Flocks also varied across latitude and disturbance gradients as predicted, but effect sizes were small. Our findings indicate that the unstructured nature of Andean flocks might arise as a strategy to cope with harsh environmental conditions. This article is part of the theme issue ‘Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes’.

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Background Urbanization will increase in the next decades, causing the loss of green areas and bird diversity within cities. There is a lack of studies at a continental scale analyzing the relationship between urban green areas, such as parks and cemeteries, and bird species richness in the Neotropical region. Bird diversity-environment relationships in urban parks and cemeteries may be influenced by latitudinal gradients or species-area relationships. However, the seasonal variation of species diversity- environment has not been analyzed at a continental scale in the Neotropics. Methods Bird surveys were conducted in 36 cemeteries and 37 parks within 18 Neotropical cities during non-breeding and breeding seasons. Bird diversity was assessed through Hill numbers, focusing on species richness, the effective number of species derived from Shannon index and the Simpson index. Environmental variables included latitude, altitude, and local scale variables such as area size, habitat diversity and pedestrian traffic. Results Species richness and Shannon diversity were higher during the breeding season, whereas Simpson diversity did not vary between seasons. During both seasons, species richness increased with area size, was negatively related to altitude, and was the highest at 20° latitude. Species richness was also positively related to habitat diversity, pedestrian traffic, and was highest in suburban areas during the non-breeding season. Shannon and Simpson diversity showed significant relationships with habitat diversity and area size during the breeding season. Bird diversity was similar between parks and cemeteries. Discussion Our results showed that urban parks and cemeteries have similar roles in conserving urban bird diversity in Neotropical cities. However, species diversity-environment relations at the continental scale varied between seasons, highlighting the importance of conducting annual studies.

As the scientific environment is hierarchical and meritocratic, greater dedication will lead to higher performance. Consequently, scientists with caregiving responsibilities will suffer downfalls in performance. Caregivers are mainly women so their career is more affected than their male counterparts’. Based on a self-perception survey among Argentinean ecologists, we studied the distribution of caregiving responsibilities, uninterrupted time dedicated to work, career paths, perception of researchers’ own work and that of others in relation to gender, and reciprocal effect between family and work. We found that a larger percentage of women carry caregiving duties, dedicate less uninterrupted time to work, and more to non-work-related tasks, especially when working from home. We found no effect of caregiving on age at promotion, although women tend to start earlier stages of their careers younger than men, while the trend reverts in later categories. Women tend to value their own work more poorly than men, and both female and male researchers tend to choose male over female referents and advisers, especially among older generations. The interaction between family and work is perceived negatively by women in early career stages. In general, women and men felt supported by their advisers with respect to family-related issues. Caregiving duties must be considered when evaluating a researcher’s performance, especially for women. Public policies must help relieve women from heavy caregiving tasks and facilitate leaving their home space to detach from not-work-related tasks. Greater peer recognition of women’s research should increase their participation as advisers and referents, as well as their own perception of their work and those of other women. We must actively propose policies that will turn academy into a fairer and more equitable working environment for women.